Yazar "Akbulut Özen, Songül" seçeneğine göre listele

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    Comparison of active and passive radon survey in cave atmosphere, and estimation of the radon exposed dose equivalents and gamma absorbed dose rates
    (Taylor & Francis Ltd, 2019) Akbulut Özen, Songül; Cevik, Ugur; Taskin, Halim
    Radon (Rn-222) measurements were conducted in the Pileki Cave with Radim 3A Active Radon Monitor equipment. Measurements were also done with the passive sampling method with CR-39 nuclear track detectors by exposing them for three months in the cave. Radon concentrations obtained from the active and passive sampling methods showed that, firstly, the concentrations inside the cave measured by the latter method differed greatly due to high humidity levels up to 88%. The total inside radon exposure dose equivalent people were subjected to was estimated to be 19 mu Sv a(-1) for visitors and 24,065 mu Sv a(-1) for guides. The gamma absorbed dose rates were determined for inside and outside the cave. The dose rates were calculated by means of using the Ra-226, Th-232 and K-40 activity concentrations and by means of real-time measurements. The gamma absorbed dose rates were found to be much higher than the value of 55 nGy h(-1) given by UNSCEAR. In addition, the mineralogical compositions and elemental analyses of samples taken from the cave were determined by XRD and WD-XRF methods.
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    Estimation of radon flux spatial distribution in Rize, Turkey by the artificial neural networks method
    (Pergamon-Elsevier Science Ltd, 2019) Yesilkanat, Cafer Mert; Akbulut Özen, Songül
    In this study, average radon flux distribution in the Rize province (Turkey) was estimated by the artificial neural networks (ANN) method. For this purpose, terrestrial gamma dose rate (TGDR), which is defined as an important proxy in determining radon flux distribution, was used. Input parameters that were used for ANN were the natural radionuclide (U-238, Th-232 and K-40) activity values in soil samples taken from 64 stations in Rize Province, data from ambient gamma dose rates (AGDR) directly affecting the distribution of radon flux and data of geographical coordinates. Randomly chosen 42 stations were used for ANN training and data from 22 stations were used for testing the ANN model. Performance test results gave a Pearson's r value of 0.60 (p < 0.001) and RMSE of 0.296. The area that was used for the model was divided into grids of 100 m by 100 m and a spatial distribution map was composed by using ANN predicted radon flux rates at grid nodes, whereby natural radionuclide values and Ordinary Kriging predicted values of external gamma dose rates were used for composing the map.
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    Indoor and outdoor radon measurements at lung cancer patients' homes in the dwellings of Rize Province in Turkey
    (Springer, 2018) Akbulut Özen, Songül; Celik, Necati; Dursun, Emrehan; Taskin, Halim
    In this study, indoor and outdoor radon (Rn-222) surveys were carried out in the summer and winter seasons in homes of one hundred lung cancer patients in the year 2013-2014. The aim was to investigate the relationship between radon and cancer patients. Lung cancer patients completed a questionnaire concerning their living environment, various physical parameters and living habits. Pearson correlation and t tests revealed no meaningful results between radon concentrations, on one hand, and environmental and personal living habits, on the other hand. Consequently, the BEIR VI model was adapted and Rn-222 exposure was estimated to be responsible for about 12% of the lung cancer incidences in the winter season and around 5% in the summer season in the Rize Province. However, due to the limited number of data and numerous parameters that could lead to lung cancer, the estimations done with the model should be taken very lightly. The annual effective doses due to inhalation of indoor and outdoor Rn-222 were estimated to be, respectively, 1.43 and 0.94 mSv y(-1). The indoor and outdoor annual effective doses were, respectively, close and below the world annual effective dose (1.3 mSv y(-1)). At the district level, the indoor annual effective dose equivalent in the A degrees yidere district was 4.52 mSv y(-1), which was 3.5 times greater than the world average. The number of patients in the majority of the houses in this district was more than one.
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    Investigation of heavy metal distributions along 15m soil profiles using EDXRF, XRD, SEM-EDX, and ICP-MS techniques
    (Wiley, 2018) Akbulut Özen, Songül; Ozkalayci, Fatih; Cevik, Ugur; Van Grieken, Rene
    The research of soil contamination by heavy metal is an important field due to its environmental and health implications. The goal was to study the elemental mobility as a function of depth. For this reason, the distribution of heavy metals (V, Cr, Co, Ni, Cu, Zn, As, Sn, and Pb) was investigated along soil profiles up to a depth of 15m at 9 sampling sites in the Nilufer industrial district (Bursa, Turkey). Elemental analyses were done with the Epsilon 5 energy dispersive X-ray fluorescence and inductively coupled plasma mass spectrometry equipment. Particle analysis was performed with a JEOL scanning electron microscope equipped with a Si(Li) X-ray detector. The crystallographic compositions of oxide compounds in soil samples were identified by a Rigaku X-ray diffraction instrument. Different parameters such as the soil's chemical (mineralogical structure, pH, and electrical conductivity) and physical properties (the number of blows, the stiffness index, the liquidity index, the plasticity index, and the water content) were analyzed. To assess the mobility of the heavy metals, diffusion (D) and convection coefficients (?) were calculated with the finite difference method. Convection was determined to dominate the studied region. In addition, the mobility coefficient was determined for each metal. High mobilities were determined for Zn and V, moderate mobilities for Cr, Ni, Cu, and As, and low mobilities were determined for Co and Pb. The results revealed that elements had reached depths of up to 15m, causing irreversible soil contamination that may lead to environmental health issues.
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    Isolated solar electronic unit design including capacitive storage for the uninterruptible power supply of critical DC loads
    (Pergamon-Elsevier Science Ltd, 2021) Özküçük, Serhat; Akbulut Özen, Songül
    In this study, to the aim was to design an isolated, reliable and efficient DC-DC (flyback based) photovoltaic energy sourced supply unit, which has its own electrolyte-super capacitor based energy storage unit in order to compensate for disruptions and failures that can occur in photovoltaic solar panels. In this storage unit, a hierarchical charging structure has been developed for eliminating the drawbacks of battery technologies such as cooling issues, chemical dangers, heavy weight, charging and discharging current/voltage limitations. The designed supply unit is capable of operating in a wide range of input voltages for the supply of important and expensive solar-based photovoltaic subsystems. Also, it was designed to supply a steady and balanced power to control systems that have microcontrollers or expensive control elements for different purposes up to 50 W. The design can be considered as a model for an uninterruptible power supply with a specific capacitive storage. The designed unit has important advantages due to its large usage area, especially microgrid and off-grid systems, its low cost and less complex construction. The designed hierarchical charging super capacitor based energy storage unit in this study is expected to have important implications for future research due to its possibility to be developed in accordance with different environmental conditions and objectives.
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    Numerical simulation of a parabolic trough collector containing a novel parabolic reflector with varying focal length
    (Pergamon-Elsevier Science Ltd, 2019) Külahlı, Mehmet Canalp; Akbulut Özen, Songül; Etemoglu, Akin Burak
    In this study, a novel parabolic reflector for a Parabolic Trough Collector (PTC) is presented. The reflector contains a varying focal length in lengthwise direction while still maintaining a fixed focal line. Due to this geometry, heat flux around the absorber not only varies circumferentially but also axially. A new geometric design parameter is defined which is the ratio of focal length at the ends, and the effects of it on the thermal behavior are investigated numerically. To represent the heat flux realistically a method is presented by employing a custom code to construct the novel reflector in SolTrace (a ray tracing software), and heat flux profile around the absorber is calculated. This flux is applied to a Computational Fluid Dynamics (CFD) model as a source term and simulations are realized. The coupled model is validated with the experimental results regarding the LS-2 module. Besides the parametric analyses about geometric factor, flow rate optimization analyses are also. As a result of the parametric analyses, a 0.21% rise is achieved for thermal efficiency and a 0.63% increase is achieved for net energy gain as a result of the flow rate optimization study.
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    Study of the hydrothermal crystallization process of barium titanate by means of X-ray mass attenuation coefficient measurements at an energy of 59.54 keV
    (Elsevier Science Inc, 2017) Akbulut Özen, Songül; Ozen, Murat; Sahin, Mehmet; Mertens, Myrjam
    In this work, the X-ray mass attenuation coefficients of hydrothermally synthesized barium titanate (BaTiO3) samples were calculated with the purpose of determining the crystallization sequence of BaTiO3. Hydrothermally synthesized samples prepared at 100 degrees C and 200 degrees C, and reacted for varying reaction times between 15 min up to 120 h were studied. Attenuation coefficient measurements were done with a coaxial HPGe gamma detector (Ortec, GEM55P4-95) with a working range in the X-ray energy region. The samples were made into pellets and were exposed to Am-241 radioisotopes at an energy of 59.54 keV for 300 s. Additionally, FT-Raman and XRD measurements were done to support the X-ray mass attenuation measurements. It was found that secondary barium titanate (BT) phases (BaTi2O5 and Ba2TiO4) were formed from the precursor material at the early stages of the hydrothermal reaction and that phase pure BaTiO3 was formed at longer reaction times. The sequence of barium titanate crystallization was determined as follows: BaTi2O5; BaTi2O5 and BaTiO3; BaTi2O5, Ba2TiO4 and BaTiO3: and phase pure BaTiO3.
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    The effect of energy resolution of detection instrument on mass attenuation coefficient
    (Iop Publishing Ltd, 2018) Celik, N.; Akbulut Özen, Songül; Demirtas, O. F.; Cevik, U.
    The effect of energy resolution of two detection systems, HPGe and NaI(T1), was determined by Monte Carlo (MC) calculation on mass attenuation coefficients of magnesium (Mg) and tungsten (W). In order to reveal the energy resolution effect, the detectors' collimator diameters were changed from 2 mm to 20 mm while sending collimated photon beams to the absorber material. It was observed that mass attenuation coefficients were increased with increasing collimator diameters. The performances of HPGe and NaI(T1) detectors were quantified. The calculated results were compared with experimental results for Mg at energy of gamma rays 662 keV for different collimator diameters using both HPGe and NaI(T1). It was observed that the MC calculation results were in a good agreement with the experimental data within the relative error from around 4% to 8%.