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Use of Polymer Fibers Recovered from Waste Timing Belts in High Performance Concrete
, M.Sc. Thesis Sharif University of Technology ; Khalu, Alireza (Supervisor)
Abstract
The present paper discusses the possibility of adding recycled polymer fibres to high performance concrete (HPC). Fibres used in this study were recovered from discarded car timing belts. To investigate different characteristics of the concrete specimens several destructive and non-destructive tests, such as compressive strength, modulus of rupture, flexural toughness, ultrasonic velocity and electrical resistance tests were carried out. In addition, slump flow tests were conducted on the fresh concrete. Experimental results from the study showed that the use of low percentages (up to 0.5%) of waste fibres improved the modulus of rupture and flexural toughness. Based on ultrasonic and...
State Feedback Control Proton Exchange Membrane Fuel Cell (Pem) Stack
, M.Sc. Thesis Sharif University of Technology ; Pishvaie, Mahmoud Reza (Supervisor)
Abstract
In recent years, fuel cells have been proposed as an alternative option to conventional energy conversion systems. Fuel cell is an electrochemical system that can convert chemical energy to electrical energy without combustion. High efficiency, low temperature performance, poor pollution, good reliability, flexibility in the production potential, low start-up time and high life expectancy are the major advantages of this system. The most important barriers to the use of fuel cells are high cost polymer membrane and using expensive platinum catalysts. Modeling of fuel cells in general will meet two objectives. The first, due to the complexity of the processes taking place within the cell,...
Mechanical properties of fiber-reinforced high-performance concrete incorporating pyrogenic nanosilica with different surface areas
, Article Construction and Building Materials ; Volume 101 , December , 2015 , Pages 130-140 ; 09500618 (ISSN) ; Khaloo, A ; Hosseini, P ; Esrafili, A ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
The aim of the present study was to investigate the effect of pyrogenic nanosilica with different specific surfaces areas (200 and 380 m2/g) on mechanical properties of fiber-reinforced high-performance concrete (FRHPC) produced with two different types of fibers including steel and polypropylene fibers. Accordingly, different mechanical tests (compressive, splitting tensile and flexural strengths) as well as electrical resistivity were performed at 7, 28, and 91 curing days. In addition, the modulus of rupture and flexural toughness of FRHPC prisms were calculated based on the flexural testing results. Also, scanning electron microscopy test (SEM) was conducted to evaluate the...
Electrochemical degradation of clindamycin by anodic oxidation on SnO2-Sb coated titanium anodes
, Article Environmental Engineering and Management Journal ; Volume 17, Issue 2 , February , 2018 , Pages 343-355 ; 15829596 (ISSN) ; Davoudi, M ; Farzadkia, M ; Esrafili, A ; Dolati, A ; Sharif University of Technology
Gheorghe Asachi Technical University of Iasi, Romania
2018
Abstract
Degradation of Clindamycin phosphate (CMP) was studied in aqueous solutions by an anodic oxidation process under galvanostatic conditions. The electrolysis cell consisted of a Ti/SnO2-Sb anode, prepared by dip-coating technique, and a 316 stainless steel cathode, both of which had a surface area of 6 cm2. The effects of critical factors, including CMP concentration, current density, initial pH, and the supporting electrolyte were evaluated. The electrochemical oxidation of CMP was controlled by mass transport within the studied range. The kinetic analysis indicated that the degradation reactions followed pseudo-first-order equation. The rate of CMP decay, as well as that of COD removal,...
Effects of nano-clay particles on the short-term properties of self-compacting concrete
, Article European Journal of Environmental and Civil Engineering ; Volume 0 - Issue 0 , Oct , 2015 , Page 1-21 ; 19648189 (ISSN) ; Afshar, A ; Vafaei, B ; Booshehrian, A ; Molaei Raisi, E ; Esrafili, A ; Sharif University of Technology
Taylor and Francis Ltd
2015
Abstract
The properties of self-compacting concrete (SCC) can be manipulated by the addition of nano-montmorillonite (NMMT) clays. This paper presents the results of an experimental investigation on incorporating small dosages of NMMT clays (.25, .50, .75 and 1.00% addition by mass of total cementitious material) into SCC. Tests were conducted on fresh and hardened specimens to measure workability (by slump flow, V-funnel and L-box), mechanical (by compressive and splitting tensile strengths), durability (electrical resistivity and water penetration) and microstructural (X-ray diffraction and scanning electron microscopy) properties of control and NMMT-reinforced SCCs. The results showed that the...
Effects of nano-clay particles on the short-term properties of self-compacting concrete
, Article European Journal of Environmental and Civil Engineering ; Volume 21, Issue 2 , 2017 , Pages 127-147 ; 19648189 (ISSN) ; Afshar, A ; Vafaei, B ; Booshehrian, A ; Molaei Raisi, E ; Esrafili, A ; Sharif University of Technology
Taylor and Francis Ltd
2017
Abstract
The properties of self-compacting concrete (SCC) can be manipulated by the addition of nano-montmorillonite (NMMT) clays. This paper presents the results of an experimental investigation on incorporating small dosages of NMMT clays (.25,.50,.75 and 1.00% addition by mass of total cementitious material) into SCC. Tests were conducted on fresh and hardened specimens to measure workability (by slump flow, V-funnel and L-box), mechanical (by compressive and splitting tensile strengths), durability (electrical resistivity and water penetration) and microstructural (X-ray diffraction and scanning electron microscopy) properties of control and NMMT-reinforced SCCs. The results showed that the...
Role of spin state on the geometry and nuclear quadrupole resonance parameters in hemin complex
, Article Biophysical Chemistry ; Volume 134, Issue 3 , 2008 , Pages 200-206 ; 03014622 (ISSN) ; van der Spoel, D ; Esrafili, M. D ; Parsafar, G. A ; Hadipour, N. L ; Sharif University of Technology
2008
Abstract
Theoretical calculations of structural parameters, 57Fe, 14N and 17O electric field gradient (EFG) tensors for full size-hemin group have been carried out using density functional theory. These calculations are intended to shed light on the difference between the geometry parameters, nuclear quadrupole coupling constants (QCC), and asymmetry parameters (ηQ) found in three spin states of hemin; doublet, quartet and sextet. The optimization results reveal a significant change for propionic groups and porphyrin plane in different spin states. It is found that all principal components of EFG tensor at the iron site are sensitive to electronic and geometry structures. A relationship between the...
Heterogeneous catalytic ozonation by Nano-MgO is better than sole ozonation for metronidazole degradation, toxicity reduction, and biodegradability improvement
, Article Desalination and Water Treatment ; Volume 57, Issue 35 , 2016 , Pages 16435-16444 ; 19443994 (ISSN) ; Bahrami Asl, F ; Farzadkia, M ; Esrafili, A ; Salahshour Arian, S ; Khazaei, M ; Dadban Shahamat, Y ; Zeynalzadeh, D ; Sharif University of Technology
Taylor and Francis Inc
2016
Abstract
Abstract: In the current paper, the removal efficiency of metronidazole (MNZ) using a catalytic ozonation process (COP) in the presence of magnesium oxide nanocrystals, as a catalyst, was investigated in deionized water and compared with a sole ozonation process (SOP). The influence of several operational factors on both removal processes was evaluated: solution pH, MgO dosage, initial MNZ concentration, and reaction time. Biodegradability improvement, mineralization rate, oxidation intermediates, and toxicity were also studied for the COP. The results showed that MgO nanocrystals accelerated MNZ removal compared to the SOP. The optimum pH for both SOP and COP was obtained at 10 and optimum...