Yazar "Dogru, Mahmut" seçeneğine göre listele

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    Physical, mechanical and neutron shielding properties of h-BN/Gd2O3/HDPE ternary nanocomposites
    (PERGAMON-ELSEVIER SCIENCE LTD, 2018) Irim, S. Gozde; Wis, Abdulmounem Alchekh; Keskin, M. Aker; Baykara, Oktay; Ozkoc, Guralp; Avci, Ahmet; Dogru, Mahmut
    In order to prepare an effective neutron shielding material, not only neutron but also gamma absorption must be taken into account. In this research, a polymer nanocomposite based novel type of multifunctional neutron shielding material is designed and fabricated. For this purpose, high density polyethylene (HDPE) was compounded with different amounts of hexagonal boron nitride (h-BN) and Gd2O3 nanoparticles having average particle size of 100 nm using melt-compounding technique. The mechanical, thermal and morphological properties of nanocomposites were investigated. As filler content increased, the absorption of both neutron and gamma fluxes increased despite fluctuating neutron absorption curves. Adding h-BN and Gd2O3 nano particles had a significant influence on both neutron and gamma attenuation properties (Sigma, cm(-1) and mu/rho cm(-2)/g) of ternary shields and they show an enhancement of 200-280%, 14-52% for neutron and gamma radiations, respectively, in shielding performance.
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    Radioactivity and hydrochemical properties of certain thermal Turkish spa waters
    (IWA PUBLISHING, 2017) Karakaya, Muazzez Celik; Dogru, Mahmut; Karakaya, Necati; Kuluozturk, Fatih; Nalbantcilar, Mahmut Tahir
    The study aims to determine the radioactivity levels of thermal waters which have been used seasonally or permanently in spas for therapeutic intentions. Samples were collected from spas in different regions of Turkey. Some radionuclides (K-40, Th-232, Ra-226, Cs-137), gross alpha (GA) and gross beta (GB) activities, and physical and some chemical parameters were measured. Gamma radiation measurements for Ra-226, Th-232 and K-40 radionuclides were performed by using a high purity germanium (HPGe) detector. The results of the gamma spectrometry ranged from 1.385 to 11.025 mBql(-1) for Ra-226, < minimum detectable activity to 3.477 mBql(-1) for 232Th and 9.679 to 36.989 mBql(-1) for K-40. GA and GB activity concentrations were detected by using ultra-low level alpha/beta counter. The GA and GB activity ranged from 43 to 3,182 mBql(-1) and 54 to 1,950 mmBql(-1), respectively. Based on calculated annual effective dose equivalent, the total dose originated mostly from Ra-226 and slightly from K-40. Furthermore, waters with high Cl content were enriched with K-40, Ra-226 isotopes, and the source of GA and GB activity in these waters was mostly Ra-226. Strong high positive correlation between Cl, Ra-226 and total dissolved solids in Cl-enriched samples indicated that the nuclides formed from dissolved minerals in these waters.
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    Radioactivity concentrations and dose assessments of therapeutic peloids from some Turkish spas
    (MINERALOGICAL SOC, 2015) Karakaya, Muazzez Celik; Dogru, Mahmut; Karakaya, Necati; Vural, Hasibe Cingilli; Kuluozturk, Fatih; Bal, Sultan Sahin
    The activity concentrations of natural radionuclides in peloids were studied to assess the radiologic hazard from 18 Turkish spas. The peloids are mainly used for therapeutic treatments, rheumatic diseases and aesthetic purposes. The concentrations of the natural radionuclides Ra-226, Th-232, K-40 and Cs-137 were determined with a gamma ray spectrometer using a HPGe detector. The average activity concentrations of Ra-226, Th-232, K-40, and Cs-137 in the peloids studied were 110.69, 71.52, 576.48 and 0.447 Bq/kg, respectively. The radium equivalent activities in the peloid samples ranged from 63.3 to 766.77 Bq/kg. The absorbed dose rate (D-out) varied between 37.52 and 330.67 nGy/h and most of the observed spa doses are greater than the worldwide recommended values. The annual effective dose values range from 0.26 to 2.78 mu Sv/y. The annual gonadal dose equivalents of the samples vary from 224.07 to 2283.55 with a mean of 821.99 mu Sv/y.