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Golsa Naderi,Ali ShokuhFar,Rahim Naghizadeh,S. Atashgar,Hamid Reza Rezaie 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.1
Tialite (Al2TiO5) is a ceramic material of very low thermal expansion coefficient, excellent thermal shock resistance, high refractoriness and good corrosion resistance. However, industrial applications of this material are hindered by two major limitations: decomposition to its parent oxides, alumina and rutile between 800 and 1280 oC and its low thermal mechanical properties. In the present study addition of talc with a good stabilizing effect has been studied on aluminum-titanate (tialite)- based ceramics. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the effect of talc on phase evolutions, sintering, and the microstructure of aluminum-titanate, and also density measurements were performed after sintering. The results showed that the presence of talc reduces the unreacted alumina and rutile significantly. The formation of Mg0.3Al1.4Ti1.3O5 and other solid solutions of MgO and aluminum-titanate were observed. Tialite (Al2TiO5) is a ceramic material of very low thermal expansion coefficient, excellent thermal shock resistance, high refractoriness and good corrosion resistance. However, industrial applications of this material are hindered by two major limitations: decomposition to its parent oxides, alumina and rutile between 800 and 1280 oC and its low thermal mechanical properties. In the present study addition of talc with a good stabilizing effect has been studied on aluminum-titanate (tialite)- based ceramics. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the effect of talc on phase evolutions, sintering, and the microstructure of aluminum-titanate, and also density measurements were performed after sintering. The results showed that the presence of talc reduces the unreacted alumina and rutile significantly. The formation of Mg0.3Al1.4Ti1.3O5 and other solid solutions of MgO and aluminum-titanate were observed.
Predicting the production rate of diamond wire saws using multiple nonlinear regression analysis
Golsa Sadegheslam,Reza Mikaei,Reza Rooki,Saleh Ghadernejad,Mohammad Ataei 한국자원공학회 2013 Geosystem engineering Vol.16 No.4
In this paper, the prediction of production rate of diamond wire saws was performed. Performance measurements of diamond wire saws were conducted on 14 different carbonate rocks in mines located in Iran. Rock samples were collected from the mines for laboratory tests. Elasticity modulus, quartz content, and uniaxial compressive strength (UCS) were determined in the laboratory. Production values were correlated with the corresponding elasticity modulus, quartz content, and UCS. The sawing speed and rock properties were evaluated using multiple nonlinear regression analysis, and the developed model was validated by statistical tests and actual data of sawing speed for four new mines. It was concluded that the sawing speed of carbonate rocks using diamond wire saws can reliably be estimated using the developed model.
Corrosion and Time Dependent Passivation of Al 5052 in the Presence of H2O2
Mohiedin Bagheri Hariri,Farhad Batmanghelich,Samin Sharifi-Asl,Yadollah Yaghoubinezhad,Golsa Mortazavi,Youngwoo Seo 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.4
Corrosion and time–dependent oxide film growth on AA5052 Aluminum alloy in 0.25M Na2SO4 solution containing H2O2 was studied using electrochemical impedance spectroscopy, potentiodynamic polarization, chronoamperometric and open circuit potential monitoring. It was found that sequential addition of H2O2 provokes passivation of AA5052 which ultimately thickens the oxide film and brings slower corrosion rates for AA5052. H2O2 facilitates kinetics of oxide film growth on AA 5052 at 25° and 60 °C which is indicative of formation of a thick barrier film that leads to an increment in the charge transfer resistance. Pitting incubation time increases by introduction of H2O2 accompanied by lower pitting and smoother surface morphologies. At short exposure (up to 8 h) to H2O2–containing solution, the inductive response at low frequencies predominantly determined the corrosion mechanism of AA5052. On the other hand, at prolonged exposure times (more than 24 h) to 0.25M Na2SO4+1vol% H2O2 solution, thicker oxide layers resulted in the mixed inductive–Warburg elements in the spectra.
Seismic mitigation of substation cable connected equipment using friction pendulum systems
Reza Karami Mohammadi,Masoud Mirtaheri,Mojtaba Salkhordeh,Erfan Mosaffa,Golsa Mahdavi,Mohammad Amin Hariri-Ardebili 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.6
Power transmission substations are susceptible to potential damage under seismic excitations. Two of the major seismic failure modes in substation supplies are: the breakage of brittle insulator, and conductor end fittings. This paper presents efficient isolation strategies for seismically strengthening of a two-item set of equipment including capacitive voltage transformer (CVT) adjacent to a Lightning Arrester (LA). Two different strategies are proposed, Case A: implementation of base isolation at the base of the CVT, while the LA is kept fixed-base, and Case B: implementation of base isolation at the base of the LA, while the CVT is kept fixed-base. Both CVT and LA are connected to each other using a cable during the dynamic excitation. The probabilistic seismic behavior is measured by Incremental Dynamic Analysis (IDA), and a series of appropriate damage states are proposed. Finally, the fragility curves are derived for both the systems. It is found that Friction Pendulum System (FPS) isolator has the potential of decreasing flexural stresses caused by intense ground motions. The research has shown that when the FPS is placed under LA, i.e. Case B (as oppose to Case A), the efficiency of the system is improved in terms of reducing the forces and stresses at the bottom of the porcelain. Several parametric studies are also performed to determine the optimum physical properties of the FPS.