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- 저자 : Tanyildizi (검색결과 3 건)
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Prediction of compressive strength of lightweight mortar exposed to sulfate attack
Harun Tanyildizi 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.2
This paper summarizes the results of experimental research, and artificial intelligence methods focused on determination of compressive strength of lightweight cement mortar with silica fume and fly ash after sulfate attack. The artificial neural network and the support vector machine were selected as artificial intelligence methods. Lightweight cement mortar mixtures containing silica fume and fly ash were prepared in this study. After specimens were cured in 20±2°C waters for 28 days, the specimens were cured in different sulfate concentrations (0%, 1% Mg〖SO〗_4^(-2), 2% Mg〖SO〗_4^(-2), and 4% Mg〖SO〗_4^(-2) for 28, 60, 90, 120, 150, 180, 210 and 365 days. At the end of these curing periods, the compressive strengths of lightweight cement mortars were tested. The input variables for the artificial neural network and the support vector machine were selected as the amount of cement, the amount of fly ash, the amount of silica fumes, the amount of aggregates, the sulfate percentage, and the curing time. The compressive strength of the lightweight cement mortar was the output variable. The model results were compared with the experimental results. The best prediction results were obtained from the artificial neural network model with the Powell-Beale conjugate gradient backpropagation training algorithm.
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Determining and Managing Fetal Radiation Dose from Diagnostic Radiology Procedures in Turkey
Mustafa Ozbayrak,Iffet Cavdar,Mehmet Seven,Lebriz Uslu,Nami Yeyin,Handan Tanyildizi,Mohammad Abuqbeitah,A. Serdar Acikgoz,Abdullah Tuten,Mustafa Demir 대한영상의학회 2015 Korean Journal of Radiology Vol.16 No.6
We intended to calculate approximate fetal doses in pregnant women who underwent diagnostic radiology procedures and to evaluate the safety of their pregnancies. We contacted hospitals in different cities in Turkey where requests for fetal dose calculation are usually sent. Fetal radiation exposure was calculated for 304 cases in 218 pregnant women with gestational ages ranging from 5 days to 19 weeks, 2 days. FetDose software (ver. 4.0) was used in fetal dose calculations for radiographic and computed tomography (CT) procedures. The body was divided into three zones according to distance from the fetus. The first zone consisted of the head area, the lower extremities below the knee, and the upper extremities; the second consisted of the cervicothoracic region and upper thighs; and the third consisted of the abdominopelvic area. Fetal doses from radiologic procedures between zones were compared using the Kruskal-Wallis test and a Bonferroni-corrected Mann-Whitney U-test. The average fetal doses from radiography and CT in the first zone were 0.05 ± 0.01 mGy and 0.81 ± 0.04 mGy, respectively; 0.21 ± 0.05 mGy and 1.77 ± 0.22 mGy, respectively, in the second zone; and 6.42 ± 0.82 mGy and 22.94 ± 1.28 mGy, respectively, in the third zone (p < 0.001). Our results showed that fetal radiation exposures in our group of pregnant women did not reach the level (50 mGy) that is known to increase risk for congenital anomalies. Fetal radiation exposure in the diagnostic radiology procedures in our study did not reach risk levels that might have indicated abortion.
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S. Buytoz,F. Dagdelen,I. N. Qader,M. Kok,B. Tanyildizi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5
Improving shape memory alloys in term of microstructural analysis is important for some related applications. In this study,three diff erent NiTiHf shape memory alloys were produced from high pure elements and by utilizing arc-melting device.The morphologies of diff erent precipitations and microstructures were analyzed by optical microscope, mapping, and EDXcompositional analysis. The DSC measurements showed that the phase transformation temperatures is increased by addingmore hafnium instead of nickel content in NiTiHf alloy, however, the enthalpy change for both endo/exothermic processwere decreased. Also, XRD analysis has been carried out for all alloys to fi nd diff erent phases, and to obtain grain size as afunction of diff erent composition of Ni and Hf elements. The oxidation shows that titanium dioxide (TiO 2 ) is spread out overthe surface, but the microstructures are completely diff erent for each case, e.g. needle-like shapes (nanorods) has extendedover the surface of Alloy A with 3 at% Hf, but plate-like Ti-rich microstructures is dominated on the surface of Alloy B thathas twice as more Hf as Alloy A; on the other hand, Alloy C with 9 at% Hf has some precipitates with TiO phase.
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