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- 저자 : Bahramifar, Amir (검색결과 3 건)
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High Deformable Concrete (HDC) element: An experimental and numerical study
Kesejini, Yasser Alilou,Bahramifar, Amir,Afshin, Hassan,Tabrizi, Mehrdad Emami Techno-Press 2021 Advances in concrete construction Vol.11 No.5
High deformable concrete (HDC) elements have compressive strength rates equal to conventional concrete and have got a high compressive strain at about 20% to 50%. These types of concrete elements as prefabricated parts have an abundance of applications in the construction industry which is the most used in the construction of tunnels in squeezing grounds, tunnel passwords from fault zones or swelling soils as soft supports. HDC elements after reaching to compressive yield stress, in nonlinear behavior have hardening combined with increasing strain and compressive strength. The main aim of this laboratory and numerical research is to construct concrete elements with the above properties so the compressive stress-strain behavior of different concrete elements with four categories of mix designs have been discussed and finally one of them has been defined as HDC element mix design. Furthermore, two columns with and without implementing of HDC elements have been made and stress-strain curves of them have been investigated experimentally. An analysis model is presented for columns using finite element method adopted by ABAQUS. The results obtained from the ABAQUS finite element method are compared with experimental data. The main comparison is made for stress-strain curve. The stress-strain curves from the finite element method agree well with experimental results. The results show that the dimension of the HDC samples is significant in the stress-strain behavior. The use of the element greatly increases energy absorption and ductility.
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K. Azizi,S. Majid Hashemianzadeh,Sh. Bahramifar 한국물리학회 2011 Current Applied Physics Vol.11 No.3
Interaction of carbon monoxide with armchair single-walled carbon nanotubes (SWCNTs) of various diameters was investigated using the B3LYP density functional theory (DFT) level. For both the external and internal cases, the effect of molecular orientation on the adsorption process was studied. The adsorption energies, equilibrium distances, HOMO―LUMO energy gaps, partial charges, and natural atomic orbital occupancies of the interacting atoms were also studied. It was found that physisorption of molecular CO via the oxygen head was stronger than that via the carbon head, and that the most favorable adsorption angle between the molecular axis and x-axis of the tubes for all the armchair nanotubes was 135°. Furthermore, stability of the tube―molecule system for adsorption of a CO molecule on the outer wall of a nanotube decreases as the tube diameter increases, regardless of the adsorption angle. In contrast, CO penetration into a nanotube depends on the adsorption angle. The results show that molecular CO could be adsorbed on the inner walls of the armchair nanotubes provided that the molecular axis and the main axis of the nanotubes are parallel to each other.
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Faezeh Mahdad,Habibollah Younesi,Nader Bahramifar,Mojtaba Hadavifar 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.6
In the present study, the application of advanced oxidation processes (AOPs) for the treatment of composting leachate by an activated sludge process was investigated. The efficiency of Fenton process and photo-Fenton process for treatment of high Chemical Oxygen Demand (COD), color and turbidity removal was investigated using Response Surface Methodology (RSM) under Central Composite Design (CCD). Optimal removal efficiencies were achieved 55.91% and 75.53% in Fenton process and 69.64 and 84.09% in a photo-Fenton process for CODCr and color removal, respectively at initial pH 4.5, hydrogen peroxide dosage 1 ml/L, iron sulfate dosage 0.75 g/L and Ultra-Violet (UV) contact time 78 min. Furthermore, results indicated that the BOD5/COD ratio was increased from 0.2 to 0.52, which in turn increases wastewater biodegradability. Results showed that initial pH in the photo-Fenton process had an enormous effect on CODCr removal efficiency. In consequence, the photo-Fenton process was more efficient process in CODCr and color removal for composting leachate.
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