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    Assessment of environmental radioactivity in soil samples from Bartin Province, Turkey
    (Springer, 2021) Ozdemir Oge, Tuba; Ozdemir, Firdevs Banu; Oge, Mecit
    The radioactivity levels in the soil samples from Bartin Province, Turkey were determined using a HPGe detector, and the hazard parameters were calculated. The mean concentration values were measured as 6 +/- 2; 7 +/- 3; 136 +/- 15; 2 +/- 1 and 8 +/- 3 Bq kg(-1), for U-238, Th-232, K-40, Cs-137 and Ra-226, respectively. The average radium equivalent, absorbed gamma dose rate, annual effective dose equivalent, external hazard index and excess lifetime cancer risk were calculated as 26.74 Bq kg(-1), 12 +/- 3 nGy h(-1), 15 +/- 3 mu Sv y(-1), 0.1 +/- 0.02 and 0.053 +/- 0.011, respectively. Amasra district exhibited the highest radiological hazard parameters which is attributed to the mining activities. All measured and calculated values were found to remain under the limit values.
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    Assessment of radioactivity from groundwater samples from selected areas of Western Black Sea Region, Turkey
    (Walter De Gruyter Gmbh, 2020) Oge, Tuba Ozdemir; Ozdemir, Firdevs Banu
    In this study, radon concentration measurements and chemical analyses of groundwater samples were performed in four sampling locations of Bartin Province of Western Black Sea Region, Turkey. Rn-222 analysis was carried out in groundwater samples with liquid scintillation counting system in accordance with ASTM D5072 standard. The pH, total hardness, alkalinity and dissolved oxygen parameters of the groundwater samples were also determined. The radon concentrations for the water samples ranged between <3.00 Bq/L-12.03 Bq/L. Thirty eight percentage of the samples slightly exceeded the permissible limit of 11.1 Bq/L specified by USEPA for drinking waters. The annual effective doses of groundwater samples were calculated in the range of 7.41-30.74 mu Sv/y for ingestion of water (E-w.Ig), and in the range of 7.31-30.31 mu Sv/y for inhalation of radon released from water (E-w.Ih). The total calculated annual effective doses due to ingestion and inhalation were found to be below the limit value of 100 mu Sv/y specified by the World Health Organization (WHO). The radioactivity measurement results significantly varied for three sampling points but not for one sampling point on two different measurement dates, which is attributed to the differences in geological structure. The chemical analysis results, except for total hardness in two sampling points, were within the permissible limits specified by international standards.
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    The evaluation of spectral transmittance of optical eye-lenses
    (Elsevier Gmbh, 2016) Ozdemir, Tuba; Saglam, Adnan; Ozdemir, Firdevs Banu; Keskiner, Ali Unsal
    In the present study, the effect of light on mineral (Quartz) and organic lenses (Diethylene glycol bis (allyl carbonate)-CR39, polycarbonate, trivex) is briefly reported. It is essential to choose the right conditions for ophthalmic lenses, such as the lighting environment in order to maintain the eye health. In this article, to discuss the harmful effects of ultraviolet radiation (UVR) on the lenses and to analyze the results of the visible-light transmittance, the properties of mineral and organic eye-lenses are investigated considering the personal eye-protections, ophthalmic optics, the transmittance requirements standards of scientific researches and the literature studies, by use of coated and uncoated prescriptive ophthalmic plastic concave and convex lenses. A UV-vis spectrophotometer device is used to determine the spectral transmittance of lenses in different diopters, index numbers and coating characteristics. Additionally, the physical and optical characteristics of eye-lenses, as well as their chemical characteristics and molecular structures are studied in this article. Also, the vibrational frequencies of organic lenses are investigated applying FT-IR device measurements, and the optimized molecular structure of CR-39 monomer by density functional theory (DFT) quantum chemical method is explained using B3LYP method with STO-3G and 6-31G as basis set. (C) 2015 Elsevier GmbH. All rights reserved.
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    Investigation of tribological properties of polypropylene (PP)- Acrylonitrile butadiene styrene (ABS) blends reinforced with graphene nano-platelets (GNPs)
    (Elsevier Sci Ltd, 2023) Karteri, Ibrahim; Oge, Mecit; Kucuk, Yilmaz; Oge, Tuba Ozdemir; Ozdemir, Firdevs Banu; Karatasli, Muhammet; Culha, Mehmet Ali
    The tribological response of PP-ABS/GNPs nanocomposites fabricated via extrusion and injection molding with varying wt% GNPs fractions were examined under varying normal load and sliding speed wear test parameters. The specimens with 3% GNPs and 11% GNPs respectively exhibited the lowest and highest specific wear rates and COF under all test conditions. Increased load led to significantly reduced COF values, whereas increased sliding speed led to a slight reduction in COF by contributing to the formation of a continuous transfer layer. Addition of GNPs helped to retain the worn material on the contact surface and led to improved wear resistance up to the weight fraction of 3% after which non-homogeneous dispersion of GNPs occurred.