Loading...
Search for:
irani-rahaghi--a
0.164 seconds
Total 14697 records
Two-dimensional numerical investigation of a micro combustor
, Article Scientia Iranica ; Volume 17, Issue 6 B , December , 2010 , Pages 433-442 ; 10263098 (ISSN) ; Saidi, M. S ; Saidi, M. H ; Shafii, M. B ; Sharif University of Technology
2010
Abstract
In this paper, a two-dimensional numerical approach is used to study the effect of micro combustor height, mass flow rate and external convection heat transfer coefficient on the temperature and species mass fraction profiles. A premixed mixture of H2-Air with a multi-step chemistry is used. The transient gas phase energy and species conservation equations result in an Advection-Diffusion-Reaction system that leads to two stiff systems of PDEs. In the present work, the computational domain is solved through the Strang splitting method, which is suitable for a nonlinear stiff system of PDEs. A revised boundary condition for the velocity equation is applied and its effect on the flow...
One Dimensional and Two Dimensional Numerical Investigation of Micro Scale Combustion
, M.Sc. Thesis Sharif University of Technology ; Saidi, Mohammad Said (Supervisor) ; Saidi, Mohammad Hasan (Supervisor) ; Shafii, Mohammad Behshad (Supervisor)
Abstract
In this paper, a one-dimensional and two-dimensional numerical approach is used to study the effect of various parameters such as micro combustor height, mass flow rate and external convection heat transfer coefficient on the temperature and species mass fraction profiles. A premixed mixture of H2-Air with a multi-step chemistry (9 species and 19 reactions) is used. The transient gas phase energy and species conservation equations result in an Advection-Diffusion-Reaction system (A-D-R) that leads to two stiff systems of PDEs, which can not be solved by conventional Computational Fluid Dynamics (CFD) methods. In the present work, Strang splitting method, which is suitable for nonlinear stiff...
An analytical and experimental study of precision forging of aluminum spur gear
, Article Steel Research International, 16 September 2012 through 19 September 2012, Krakow ; Volume SPL. ISSUE , September , 2012 , Pages 163-166 ; 16113683 (ISSN) ; 9783514007970 (ISBN) ; Taheri, A. K ; Sharif University of Technology
Wiley-VCH Verlag
2012
Abstract
An important aspect of production of gears by precision forging process is the prediction of load required to perform the process and to design the forging die. In this research a new kinematically admissible velocity field is presented to predict the forging load by an upper bound analysis. The analysis considers the shape of tooth profile, number of teeth, and frictional conditions between the die/punch and deforming material. To verify the predicted results the 7075 aluminum alloy billets were forged at temperature of 150 to 250 °C in a precision forging die designed to produce a spur gear of 5 teeth. A good agreement was found between the two sets of results at the filling stage of the...
Effect of forging temperature on homogeneity of microstructure and hardness of precision forged steel spur gear
, Article Materials Chemistry and Physics ; Volume 112, Issue 3 , 2008 , Pages 1099-1105 ; 02540584 (ISSN) ; Karimi Taheri, A ; Sharif University of Technology
2008
Abstract
Precision forging is a suitable process to produce spur gears due to its advantages such as reduction in machining time and production cost. The homogeneity in microstructure and mechanical properties of precision forging products can highly affect the performance of the gears during their service. In this research the effect of precision forging temperature on homogeneity of microstructure and hardness of forged gears of low carbon steel is studied. The microstructure and hardness map of the gears forged at a temperature range of 750-1150 °C revealed that the forging temperature of 950 °C is an optimum temperature to produce a spur five teeth gear with minimum inhomogeneity in the...
Retrofitting a steam power cycle by using water from the interstage feed water pump as reheat spray
, Article ASME Power Conference 2008, Lake Buena Vista, FL, 22 July 2008 through 24 July 2008 ; July , 2008 , Pages 23-30 ; 9780791848326 (ISBN) ; Irani Rahaghi, A ; Mousavi, M. S ; Power Division, ASME ; Sharif University of Technology
2008
Abstract
Various methods are used in thermal power plants to adjust the superheated or reheated steam temperature to a pre-determined set point, including flue gas recirculation, using tilting burners and spray of water from discharge of feed water pump, etc. In this paper, an innovative method is presented to control the reheater temperature by tapping water from an interstage of the feed water pump to control reheater temperature at the Bisotoun Power Plant (a steam cycle based power plant in the western Iran). The spray water for the superheaters is secured from the discharge of feed water pump, but interstage water, instead of gas recirculation or using tilting burner, is used to control the...
Investigation of intense femto-second laser ionization and dissociation of methane with time-dependent density-functional approach
, Article Chemical Physics Letters ; Vol. 604 , 2014 , Pages 60-67 ; ISSN: 00092614 ; Sadighi Bonabi, R ; Anvari, A ; Sharif University of Technology
2014
Abstract
Three dimensional calculations of electronic dynamics of CH4 in a strong laser field are presented with time-dependent density-functional theory. Time evolution of dipole moment and electron localization function is presented. The dependence of dissociation rate on the laser characters is shown and optimal effective parameters are evaluated. The optimum field leads to 76% dissociation probability for Gaussian envelope and 40 fs (FWHM) at 10 16 W cm-2. The dissociation probability is calculated by optimum convolution of dual short pulses. By combining of field assisted dissociation process and Ehrenfest molecular dynamics, time variation of bond length, velocity and orientation effect are...
Dissociative ionization of methane in an elliptical pulse shaped laser field
, Article Journal of Molecular Structure ; Volume 1079 , January , 2015 , Pages 454-459 ; 00222860 (ISSN) ; Sadighi Bonabi, R ; Anvari, A ; Sharif University of Technology
Elsevier
2015
Abstract
The effect of strong femto-second laser pulses on the dissociation probability of methane has been investigated analytically in various arrangements. The ellipticity dependence of the dissociation probability at intensities from 1014 W cm-2 to 1016 W cm-2 for Ti:Sapphire laser is presented. A reliable calculation of the dissociation probability based on 3D time-dependent Schrodinger equation with an improved model of time-dependent density-functional theory is presented. These calculations are carried out for three different cases of elliptically polarized laser pulse, optimum convolution of dual short pulses, and two-color mixed nonresonant laser pulses. It is found that the rescattering...
Selective photo-dissociative ionization of methane molecule with TDDFT study
, Article Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy ; Volume 171 , 2017 , Pages 325-329 ; 13861425 (ISSN) ; Anvari, A ; Sadighi Bonabi, R ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Three dimensional calculation of control dynamics for finding the optimized laser filed is formulated using an iterative method and time-dependent density functional approach. An appropriate laser pulse is designed to control the desired products in the dissociation of methane molecule. The tailored laser pulse profile, eigenstate distributions and evolution of the efficient occupation numbers are predicted and exact energy levels of this five-atomic molecule is obtained. Dissociation rates of up to 78%, 80%, 90%, and 82% for CH2 +, CH+, C+ and C++ are achieved. Based on the present approach one can reduce the controlling costs. © 2016 Elsevier B.V
Design and implementation of a dynamic-reconfigurable architecture for protocol stack
, Article 2nd IPM International Symposium on Fundamentals of Software Engineering, FSEN 2007, Tehran, 17 April 2007 through 19 April 2007 ; Volume 4767 LNCS , 2007 , Pages 396-403 ; 03029743 (ISSN); 9783540756972 (ISBN) ; Sabetghadam, S ; Rahaghi, R. Y ; Jalili, R ; Sharif University of Technology
Springer Verlag
2007
Abstract
Future communication and computation devices require mechanisms for on-the-fly reconfiguration in their protocol stack to operate in different situations and networks. This paper proposes a component-based framework for dynamic-reconfigurable protocol stack. Considering that every running protocol component communicates with at least one peer component, unlike related work our framework supports synchronous reconfiguration of two peer protocol components in two communicating protocol stacks. © Springer-Verlag Berlin Heidelberg 2007
A joint experimental and theoretical study of kinetic and mechanism of rearrangement of allyl p-tolyl ether
, Article Journal of Molecular Structure: THEOCHEM ; Volume 893, Issue 1-3 , 2009 , Pages 73-76 ; 01661280 (ISSN) ; Haqgu, M ; Talebi, A ; Gholami, M. R ; Sharif University of Technology
2009
Abstract
A joint theoretical and experimental study of the kinetic and mechanism of the rearrangement of allyl p-tolyl ether was performed in order to study the kinetic and mechanism of the reaction. Experimental studies were performed in gas phase over a temperature range of 493.15-533.15 K. The experimental Arrhenius parameters of this reaction were measured to be Ea = 36.08 kcal mol-1, ΔS# = -7.88 cal mol-1 K-1, and Log A = 11.74, experimentally. Using GC for the mixture of the reaction with and without cyclohexene demonstrated that the reaction is clean without any radical intermediates. The experimental results show that the studied reaction is unimolecular and proceeds through a concerted...
Multielectron dissociative ionization of methane and formaldehyde molecules with optimally tailored intense femtosecond laser pulses
, Article Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy ; Volume 185 , 2017 , Pages 298-303 ; 13861425 (ISSN) ; Anvari, A ; Sadighi Bonabi, R ; Monfared, M ; Sharif University of Technology
2017
Abstract
The multielectron dissociative ionization of CH4 and CH2O molecules has been investigated using optimum convolution of different dual tailored short laser pulses. Based on three dimensional molecular dynamics simulations and TDDFT approach, the dissociation probability is enhanced by designing the dual chirped-chirped laser pulses and chirped-ordinary laser pulses for formaldehyde molecule. However, it is interesting to notice that the sensitivity of enhanced dissociation probability into different tailored laser pulses is not significant for methane molecule. In this presented modifications, time variation of bond length, velocity, time dependent electron localization function and evolution...
Fabrication of novel chitosan-g-PNVCL/ZIF-8 composite nanofibers for adsorption of Cr(VI), As(V) and phenol in a single and ternary systems
, Article Carbohydrate Polymers ; Volume 224 , 2019 ; 01448617 (ISSN) ; Koushkbaghi, S ; Darabi, M ; ZabihiSahebi, A ; Askari, A ; Irani, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The chitosan-grafted-poly(N-vinylcaprolactam) (chitosan-g-PNVCL) nanofibers were synthesized via electrospinning method. ZIF-8 metal-organic frameworks nanoparticles were incorporated into the nanofibers for adsorption of Cr(VI), As(V) and phenol from water. The BET, FTIR, XRD and SEM analysis were carrfried out to obtain the characteristics of nanofibers. The optimum parameters of ZIF-8 content, pH, contact time, adsorbent dosage, and initial concentration of adsorbates on the Cr(VI), As(V) and phenol removal were studied. The reusability of synthesized nanofibers for five sorption-desorption cycles was also examined. The maximum experimental adsorption capacity of the...
Synthesis of ethyl cellulose/aluminosilicate zeolite nanofibrous membranes for oil–water separation and oil absorption
, Article Cellulose ; Volume 26, Issue 18 , 2019 , Pages 9787-9801 ; 09690239 (ISSN) ; Jamshidifard, S ; ZabihiSahebi, A ; Abouchenari, A ; Darabi, M ; Irani, M ; Sharif University of Technology
Springer Netherlands
2019
Abstract
ZSM-5 (Seolite Sconoy Mobil) aluminosilicate zeolites synthesized by the hydrothermal method were incorporated into the hydrophobic ethyl cellulose (EC) nanofibrous membrane. The performance of synthesized nanofibers was investigated for a gravity driven oil–water separation. The synthesized ZSM-5 nanozeolites and EC/ZSM-5 composite nanofibers were characterized using XRD, FESEM, XPS, FTIR and AFM analysis. The permeability of EC/ZSM-5 5 wt% for oil in water mixture was in order of n-hexane (5170 ± 60 L/m2 h) > n-heptane (4600 ± 50 L/m2 h) > cyclohexane (4350 ± 35 L/m2 h) > pump oil (3780 ± 28 L/m2 h) > lubricating oil (3200 ± 25 L/m2 h) > motor oil (2980 ± 20 L/m2 h) with a separation...
Adsorption and sustained release of doxorubicin from N-carboxymethyl chitosan/polyvinyl alcohol/poly(ε-caprolactone) composite and core-shell nanofibers
, Article Journal of Drug Delivery Science and Technology ; 2021 ; 17732247 (ISSN) ; Asefnejad, A ; Khorasani, M. T ; Saadatabadi, A. R ; Irani, M ; Sharif University of Technology
Editions de Sante
2021
Abstract
The core-shell nanofibers, produced by the coaxial electrospinning method, are good candidates for delivery of anticancer drugs due to their continuous release without initial burst release. In this work, the N-carboxymethyl chitosan (N-CMCS)-polyvinyl alcohol (PVA)/poly(ε-caprolactone) (PCL) composite and core-shell nanofibers were prepared by two-nozzle and coaxial electrospinning techniques, respectively. Doxorubicin (DOX) as an anticancer drug was loaded into the N-CMCS/PVA/PCL nanofibers fabricated by two-nozzle and coaxial electrospinning. The performance of nanofibers was compared for the adsorption and controlled release of DOX against MCF-7 breast cancer cells death in vitro. The...
Adsorption and sustained release of doxorubicin from N-carboxymethyl chitosan/polyvinyl alcohol/poly(ε-caprolactone) composite and core-shell nanofibers
, Article Journal of Drug Delivery Science and Technology ; 2021 ; 17732247 (ISSN) ; Asefnejad, A ; Khorasani, M. T ; Saadatabadi, A. R ; Irani, M ; Sharif University of Technology
Editions de Sante
2021
Abstract
The core-shell nanofibers, produced by the coaxial electrospinning method, are good candidates for delivery of anticancer drugs due to their continuous release without initial burst release. In this work, the N-carboxymethyl chitosan (N-CMCS)-polyvinyl alcohol (PVA)/poly(ε-caprolactone) (PCL) composite and core-shell nanofibers were prepared by two-nozzle and coaxial electrospinning techniques, respectively. Doxorubicin (DOX) as an anticancer drug was loaded into the N-CMCS/PVA/PCL nanofibers fabricated by two-nozzle and coaxial electrospinning. The performance of nanofibers was compared for the adsorption and controlled release of DOX against MCF-7 breast cancer cells death in vitro. The...
Adsorption and sustained release of doxorubicin from N-carboxymethyl chitosan/polyvinyl alcohol/poly(ε-caprolactone) composite and core-shell nanofibers
, Article Journal of Drug Delivery Science and Technology ; Volume 67 , 2022 ; 17732247 (ISSN) ; Asefnejad, A ; Khorasani, M. T ; Saadatabadi, A. R ; Irani, M ; Sharif University of Technology
Editions de Sante
2022
Abstract
The core-shell nanofibers, produced by the coaxial electrospinning method, are good candidates for delivery of anticancer drugs due to their continuous release without initial burst release. In this work, the N-carboxymethyl chitosan (N-CMCS)-polyvinyl alcohol (PVA)/poly(ε-caprolactone) (PCL) composite and core-shell nanofibers were prepared by two-nozzle and coaxial electrospinning techniques, respectively. Doxorubicin (DOX) as an anticancer drug was loaded into the N-CMCS/PVA/PCL nanofibers fabricated by two-nozzle and coaxial electrospinning. The performance of nanofibers was compared for the adsorption and controlled release of DOX against MCF-7 breast cancer cells death in vitro. The...
A density functional theory study of cyclization of citronellal
, Article Reaction Kinetics and Mechanism ; Vol. 37, Number 2 , May , 2012 , pp. 173-182 ; Gholami, M. R ; Irani, M ; Siadati, A ; Sharif University Of Technology
2012
Abstract
A theoretical study of the kinetics and mechanism of the cyclization of citronellal in the gas phase was performed using density functional theory methods at the B3LYP level of theory with 6-311G, 6-311G*, 6-31G**, 6-311G**, 6-311 þ G and 6-311 þ þ G basis sets at 298.15 K, 433.15 K, and 473.15 K. Equilibrium molecular geometries and harmonic vibrational frequencies of the reactant, transition state and products were calculated. Rate constants and activation thermodynamic parameters were calculated and showed a fairly good agreement with experimental results. The effect of solvent polarity on the reaction was studied. These calculations indicated that the reaction proceeds through an...
A Study on the effects of thermodynamic nonideality and mass transfer on multi-phase hydrodynamics using CFD methods
, Article World Academy of Science, Engineering and Technology ; Volume 58 , 2009 , Pages 627-632 ; 2010376X (ISSN) ; Bozorgmehry Boozarjomehry, R ; Pishvaie, M. R ; Tavasoli, A ; Sharif University of Technology
2009
Abstract
Considering non-ideal behavior of fluids and its effects on hydrodynamic and mass transfer in multiphase flow is very essential. Simulations were performed that takes into account the effects of mass transfer and mixture non-ideality on hydrodynamics reported by Irani et al. In this paper, by assuming the density of phases to be constant and Raullt's law instead of using EOS and fugacity coefficient definition, respectively for both the liquid and gas phases, the importance of non-ideality effects on mass transfer and hydrodynamic behavior was studied. The results for a system of octane/propane (T=323 K, P =445 kpa) also indicated that the assumption of constant density in simulation had...
Efficient high harmonic generation of bromine molecule by controlling the carrier-envelope phase and polarization of driving laser pulse
, Article Chemical Physics Letters ; Volume 719 , 2019 , Pages 27-33 ; 00092614 (ISSN) ; Monfared, M ; Sharif University of Technology
Elsevier B.V
2019
Abstract
The generation of ultrashort attosecond pulse requires both an enhanced high harmonic generation and the spectral-phase control. In the present work, an efficient method is theoretically investigated for extending HHG cutoff energy in Br2 molecule using TDDFT. The effects of molecular orientation and carrier-envelope phase of the laser on the high harmonic spectrum are analyzed. As a result, by the fine modulations of the laser field, the harmonic plateau is enlarged and the position of structure-induced interference minimum shifts. We also provide a physical picture on the intensity dependence of the spectral minima in the harmonic spectra
2D and 3D simulation of bubble columns using CFD methods
, Article CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Prague, 27 August 2006 through 31 August 2006 ; 2006 ; 8086059456 (ISBN); 9788086059457 (ISBN) ; Bozorgmehri, R ; Sharif University of Technology
2006
Abstract
This article presents the results of 2D and 3D simulations of a bubble column reactor at steady state conditions and low gas flow rates. The simulations have been done based on a two-fluid model with a k - ε model used for turbulence modeling. The experimental data have been obtained by differential pressure transducer. For analyzing of hydrodynamic parameters such as hold up and velocity profiles of phases, a system consists of water tank and air aerated from bottom is set up. The simulations have been done based on two different approaches which are mixture and eulerian approaches. Despite the fact that these approaches lead to similar results, the convergence and stability of eulerian...