Loading...
Search for:
sadeghi--ahmad
0.156 seconds
Total 1119 records
Simulation of wetting tendency of fluids with high density ratios using RK Lattice Boltzmann method
, Article 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019, 14 October 2019 through 18 October 2019 ; 2020 ; Pak, A ; Sadeghi, H ; Sharif University of Technology
Asian Regional Conference on Soil Mechanics and Geotechnical Engineering
2020
Abstract
Several lattice Boltzmann models for multi-phase flow have been developed, but few of them are capable of modeling fluid flows with high density ratio in the order of 1000. Therefore, an advanced chromodynamics, Rothmann-Keller (RK) type model is employed in current study, which can handle liquid-gas density ratio in the order of 1000 and viscosity ratio in the order of 100. Other distinctive characteristics of the proposed model are high stability, and capability of setting parameters such as surface tension independently. In spite of these benefits, the original RK model fails to model wetting tendency of the fluids. As a result, it is impossible to correctly simulate two-fluid phase flow...
Mechanical behavior during aging of plastically deformed AA6061-SiCp composite in different temperatures
, Article Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications ; Volume 226, Issue 4 , 2012 , Pages 322-329 ; 14644207 (ISSN) ; Serajzadeh, S
SAGE
2012
Abstract
In this study, the kinetics of aging in AA6061 and AA6061 with 5% volume fraction SiCp were studied and compared. The composite was first produced and homogenized using stir casting technique followed by hot extrusion with the ratio of 18:1. Then, both AA6061 and the composite were aged at three different temperatures including room temperature, 170 °C and 240 °C, while mechanical properties during aging were evaluated employing hardness measurements and tensile testing. Moreover, in order to assess the effect of plastic deformation on the kinetics of aging, a series of samples were first deformed by equal-channel angular pressing immediately after solution treatment and then aged in the...
Electroosmotic flow and ionic conductance in a pH-regulated rectangular nanochannel
, Article Physics of Fluids ; Volume 29, Issue 6 , 2017 ; 10706631 (ISSN) ; Saidi, M. H ; Sadeghi, A ; Sharif University of Technology
2017
Abstract
Infinite series solutions are obtained for electrical potential, electroosmotic velocity, ionic conductance, and surface physicochemical properties of long pH-regulated rectangular nanochannels of low surface potential utilizing the double finite Fourier transform method. Closed form expressions are also obtained for channels of large height to width ratio for which the depthwise variations vanish. Neglecting the Stern layer impact, the effects of EDL (Electric Double Layer) overlap, multiple ionic species, and association/dissociation reactions on the surface are all taken into account. Moreover, finite-element-based numerical simulations are conducted to account for the end effects as well...
Experimental Study and Modeling of Rheological Behavior of Crude Oils and W/O Emulsions in the Presence of Surfactants
,
M.Sc. Thesis
Sharif University of Technology
;
Ramazani Saadatabadi, Ahmad
(Supervisor)
;
Taghikhani, Vahid
(Supervisor)
;
Ghotbi, Cyrus
(Supervisor)
Abstract
Understanding the properties of crude oil and the phenomena arising from this precious matter has always been of considerable importance. One of these important phenomena is emulsion, which is well-known in a great number of crude oil-related processes such as drilling, well completion, production, transportation and even the processing units in the refinery. One of the most important properties of crude oils and their emulsions is their flow or in other words their rheology. Therefore, in this project has also been tried to investigate the rheological behavior of crude oil and water in crude oil emulsion, experimentally and theoretically. The experiments were carried out using two crude...
Geotechnical characterization and collapsibility of a natural dispersive loess
, Article Engineering Geology ; Volume 250 , 2019 , Pages 89-100 ; 00137952 (ISSN) ; Kiani, M ; Sadeghi, M ; Jafarzadeh, F ; Sharif University of Technology
Elsevier B.V
2019
Abstract
During preliminary investigation phase of the national Chabahar-Zahedan railway line, serious geotechnical problems including non-uniform settlements, tensile cracks, and local collapse were reported in parts of the path near the coastline. A follow-up field investigation revealed that the in-situ soil at construction site has a metastable structure being sensitive to saturation and loading. Therefore, a comprehensive series of physical, chemical, electro-chemical, and geotechnical tests were conducted to classify and characterize the soil properties and behavior in its natural state. The natural soil was classified as a clayey loess with moderately dispersive to dispersive characteristics....
Geometry effect on electrokinetic flow and ionic conductance in pH-regulated nanochannels
, Article Physics of Fluids ; Volume 29, Issue 12 , 2017 ; 10706631 (ISSN) ; Saidi, M. H ; Moosavi, A ; Sadeghi, A ; Sharif University of Technology
2017
Abstract
Semi-analytical solutions are obtained for the electrical potential, electroosmotic velocity, ionic conductance, and surface physicochemical properties associated with long pH-regulated nanochannels of arbitrary but constant cross-sectional area. The effects of electric double layer overlap, multiple ionic species, and surface association/dissociation reactions are all taken into account, assuming low surface potentials. The method of analysis includes series solutions which the pertinent coefficients are obtained by applying the wall boundary conditions using either of the least-squares or point matching techniques. Although the procedure is general enough to be applied to almost any...
Unsteady solute dispersion by electrokinetic flow in a polyelectrolyte layer-grafted rectangular microchannel with wall absorption
, Article Journal of Fluid Mechanics ; Volume 887 , 2020 ; Saidi, M. H ; Moosavi, A ; Sadeghi, A ; Sharif University of Technology
Cambridge University Press
2020
Abstract
The dispersion of a neutral solute band by electrokinetic flow in polyelectrolyte layer (PEL)-grafted rectangular/slit microchannels is theoretically studied. The flow is assumed to be both steady and fully developed and a first-order irreversible reaction is considered at the wall to account for probable surface adsorption of solutes. Considering low electric potentials, analytical solutions are obtained for electric potential, fluid velocity and solute concentration. Special solutions are also obtained for the case without wall adsorption. To track the dispersion properties of the solute band, the generalized dispersion model is adopted by considering the exchange, the convection and the...
Dispersivity, collapsibility and microstructure of a natural dispersive loess from Iran
, Article 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019, 14 October 2019 through 18 October 2019 ; 2020 ; Nasiri, H ; Panahi, P. A ; Sadeghi, M ; Sharif University of Technology
Asian Regional Conference on Soil Mechanics and Geotechnical Engineering
2020
Abstract
A new type of collapsible soil was encountered in Southern Iran and caused some serious technical problems including subsidence, collapse and sinkholes during the construction of Zahedan-Chabahar railway. Field observations indicated that in-situ soil contains excessive amount of salts resulting in dispersive features in response to seepage forces in addition to its collapsibility. Therefore, a systematic research plan including field sampling and laboratory testing was carried out to investigate the observed geotechnical features. Results of physio-chemical tests revealed the dominance of Sodium in excess of 70% relative to total dissolved salts, which results in high dispersive potential....
Modified carrageenan. 5. Preparation, swelling behavior, salt- and pH-sensitivity of partially hydrolyzed crosslinked carrageenan-graft-polymethacrylamide superabsorbent hydrogel [electronic resource]
, Article Polymers for Advanced Technologies ; Volume 15, Issue 11, pages 645–653, November 2004 ; Sadeghi, M ; Hosseinzadeh, H
Abstract
The polysaccharide, kappa-carrageenan (κC) was chemically modified to achieve a novel superabsorbent hydrogel via graft copolymerization of methacrylamide (MAM) onto the substrate followed by alkaline hydrolysis. Ammonium persulfate (APS) and N,N′-methylene bisacrylamide (MBA) were used as a free-radical initiator and a crosslinker, respectively. The saponification reaction was carried out using sodium hydroxide aqueous solution. Either κC-g-PMAM or hydrolyzed κC-g-PMAM (PMAM: polymethacrylamide) was characterized by FT-IR spectroscopy. The effect of grafting variables (i.e. concentration of MBA, MAM, and APS) and alkaline hydrolysis conditions (i.e. NaOH concentration, hydrolysis time and...
Manufacture of Smart Drug Delivery System with UCST Polymers
, M.Sc. Thesis Sharif University of Technology ; Ramazani, Ahmad (Supervisor)
Abstract
Smart heat-sensitive polymers play a unique role in drug delivery systems due to reversible behavior in response to environmental changes, especially temperature changes. Among the heat-sensitive polymers, UCST polymers due to their specific behavior and very little-known polymers with this feature are the subject of many new researches. In the present study, New designed temperature-sensitive polymers with UCST capability based on acrylamide and vinyl acetate were synthesized. These copolymers were synthesized in different percentages of acrylamide by free radical polymerization in solution conditions. All polymers compounds were characterized by H-NMR, FT-IR, DSC and GPC measurements. The...
Optimizing a bi-objective inventory model of a three-echelon supply chain using a tuned hybrid bat algorithm
, Article Transportation Research Part E: Logistics and Transportation Review ; Vol. 70, issue. 1 , October , 2014 , p. 274-292 ; Mousavi, S. M ; Niaki, S. T. A ; Sadeghi, S ; Sharif University of Technology
2014
Abstract
This paper presents a bi-objective VMI problem in a single manufacturer-single vendor multi-retailer (SM-SV-MR) supply chain, which a redundancy allocation problem is incorporated. In the hybridized problem, a manufacturer produces a single item using several machines that work in series, and stores it in a warehouse to replenish one vendor who delivers it to several retailers using the shortest possible route. A novel meta-heuristic, called hybrid bat algorithm (HBA), with calibrated parameters is utilized to find a near-optimum solution. To show the efficiency of HBA, the results are compared to the ones using the traditional BA and a genetic algorithm
Optimizing a multi-vendor multi-retailer vendor managed inventory problem: Two tuned meta-heuristic algorithms
, Article Knowledge Based Systems ; Volume 50 , September , 2013 , Pages 159-170 ; 09507051 (ISSN) ; Mousavi, S. M ; Niaki, S. T. A ; Sadeghi, S ; Sharif University of Technology
2013
Abstract
The vendor-managed inventory (VMI) is a common policy in supply chain management (SCM) to reduce bullwhip effects. Although different applications of VMI have been proposed in the literature, the multi-vendor multi-retailer single-warehouse (MV-MR-SW) case has not been investigated yet. This paper develops a constrained MV-MR-SW supply chain, in which both the space and the annual number of orders of the central warehouse are limited. The goal is to find the order quantities along with the number of shipments received by retailers and vendors such that the total inventory cost of the chain is minimized. Since the problem is formulated into an integer nonlinear programming model, the...
Optimising multi-item economic production quantity model with trapezoidal fuzzy demand and backordering: Two tuned meta-heuristics
, Article European Journal of Industrial Engineering ; Volume 10, Issue 2 , 2016 , Pages 170-195 ; 17515254 (ISSN) ; Niaki, S. T. A ; Malekian, M. R ; Sadeghi, S ; Sharif University of Technology
Inderscience Enterprises Ltd
2016
Abstract
In this paper, a multi-item economic production quantity model with fuzzy demand is developed in which shortages are backordered and the warehouse space is limited. While the demand is assumed to be a trapezoidal fuzzy number, the centroid defuzzification method is used to defuzzify fuzzy output functions. The Lagrangian relaxation procedure is first employed to solve the problem. Then, the model is extended to a constrained fuzzy integer nonlinear programming, in order to suit real-world situations. As the extended model cannot be solved in a reasonable time using exact methods, two meta-heuristic algorithms, named the genetic algorithm (GA) and the particle swarm optimisation (PSO) each...
Numerical study of lorentz force interaction with micro structure in channel flow
, Article Energies ; Volume 14, Issue 14 , 2021 ; 19961073 (ISSN) ; Ali, K ; Ahmad, S ; Cai, J ; Sharif University of Technology
MDPI AG
2021
Abstract
The heat transfer Magnetohydrodynamics flows have been potentially used to enhance the thermal characteristics of several systems such as heat exchangers, electromagnetic casting, adjusting blood flow, X-rays, magnetic drug treatment, cooling of nuclear reactors, and magnetic devices for cell separation. Our concern in this article is to numerically investigate the flow of an incompressible Magnetohydrodynamics micropolar fluid with heat transportation through a channel having porous walls. By employing the suitable dimensionless coordinates, the flow model equations are converted into a nonlinear system of dimensionless ordinary differential equations, which are then numerically treated for...
Electrokinetic Flow in pH-Regulated Solid-State/Soft Micro-Nanochannels
,
Ph.D. Dissertation
Sharif University of Technology
;
Saeedi, Mohammad Hassan
(Supervisor)
;
Mousavi, Ali
(Co-Supervisor)
;
Sadeghi, Arman
(Co-Supervisor)
Abstract
In recent years, advances have been made in the field of miniaturization of the devices (in order to increase their efficiency, lessen the materials needed for the constructions and experiments, reduce costs and energy usage) resulting in the dramatic increase of surface to volume ratio in these devices. This progress has led to the dominance of surface forces which can be used to control very important interface phenomena having a special application such as electrokinetic. Using today’s manufacturing technology; it is possible to construct micro-nanochannels made from different materials such as silicon, glass, quartz, polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA) whose...
A numerical approach for analyzing the electromagnetohydrodynamic flow through a rotating microchannel
, Article Arabian Journal for Science and Engineering ; Volume 48, Issue 3 , 2023 , Pages 3765-3781 ; 2193567X (ISSN) ; Ahmad, A ; Ahmad, S ; Ahmad, S ; Jamshed, W ; Sharif University of Technology
Institute for Ionics
2023
Abstract
The purpose of the paper is to develop a mathematical foundation for exploring the complex interaction of Coriolis and Lorentz forces with the electromagnetohydrodynamic (EMHD) flow of a power-law fluid inside a microchannel with wall slip condition. Both the Lorentz and Coriolis forces act orthogonally to each other. Mathematical modeling of the problem is based on a set of classical Maxwell and Navier–Stokes equations, which are subsequently solved numerically by employing an implicit finite difference methodology. The numerical solution thus obtained has been found to be in an excellent agreement correlation with the ones reported in the scientific literature, for some limiting cases. A...
A fresh insight into the non-linear vibration of double-tapered atomic force microscope cantilevers by considering the Hertzian contact theory
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 225, Issue 1 , 2011 , Pages 233-247 ; 09544062 (ISSN) ; Zohoor, H ; Sharif University of Technology
2011
Abstract
The non-linear flexural vibration for a double-tapered atomic force microscope cantilever has been investigated by using the Timoshenko beam theory. In this article, the normal and tangential tip-sample interaction forces are found from the Hertzian contact model, and the effects of the contact position, normal and lateral contact stiffness, height of the tip, thickness of the beam, angle between the cantilever and the sample surface, and breadth and height taper ratios on the non-linear frequency to linear frequency ratio have been studied. The differential quadrature method is employed to solve the non-linear differential equations of motion. The results show that the softening behaviour...
A new ensemble method for feature ranking in text mining
, Article International Journal on Artificial Intelligence Tools ; Volume 22, Issue 3 , June , 2013 ; 02182130 (ISSN) ; Beigy, H ; Sharif University of Technology
2013
Abstract
Dimensionality reduction is a necessary task in data mining when working with high dimensional data. A type of dimensionality reduction is feature selection. Feature selection based on feature ranking has received much attention by researchers. The major reasons are its scalability, ease of use, and fast computation. Feature ranking methods can be divided into different categories and may use different measures for ranking features. Recently, ensemble methods have entered in the field of ranking and achieved more accuracy among others. Accordingly, in this paper a Heterogeneous ensemble based algorithm for feature ranking is proposed. The base ranking methods in this ensemble structure are...
Non-linear vibration of dagger-shaped atomic force microscope cantilevers by considering the Hertzian contact theory
, Article Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics ; Volume 225, Issue 2 , 2011 , Pages 77-94 ; 14644193 (ISSN) ; Zohoor, H ; Sharif University of Technology
2011
Abstract
The non-linear flexural vibration for a dagger-shaped atomic force microscope cantilever has been investigated using the Timoshenko beam theory. In this article, the normal and tangential tip-sample interaction forces are found from Hertzian contact model and the effects of the geometry, normal and lateral contact stiffness, height of the tip, thickness of the beam, the angle between the cantilever and the sample surface and breadth and height taper ratios on the non-linear frequency to linear frequency ratio have been studied. The differential quadrature method (DQM) is employed to solve the non-linear differential equations of motion. The results show that the softening behaviour is seen...
A simplified method for computation of scattered fields by the lamp-posts along a boulevard used for wireless communications in 2-GHZ band
, Article 2010 10th Mediterranean Microwave Symposium, MMS 2010, 25 August 2010 through 27 August 2010 ; August , 2010 , Pages 346-350 ; 9781424472437 (ISBN) ; Farzaneh, F ; Sharif University of Technology
2010
Abstract
In this paper a simplified object specific ray tracing method is proposed to solve the important propagation problem of scattering by the lamp-posts. In fact, radiation from the transmitter antenna is modeled with a two ray incidence model and unknown currents on lamp-posts are computed using the Multi-Level Fast Multi-pole Method (MLFMM) which is an extension of the MoM (Method of Moments). In addition, scattering by lamp-posts is computed using the superposition of current elements electric fields based on the discrete complex image method (DCIM) in presence of a real ground with complex relative permittivity. The scattered near fields are considered instead of far fields. Based on this...