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    Shear-rate dependence modeling of gelcast slurries: Effects of dispersant content and solid loading

    , Article Ceramics International ; Vol. 40, issue. 1 PART A , 2014 , pp. 123-128 ; ISSN: 02728842 Nojoomi, A ; Faghihi-Sani, M. A ; Khoshkalam, M ; Sharif University of Technology
    Gelcasting, as a ceramic forming technique, is getting worldwide attention, in that it can be used to make high-quality, complex-shaped ceramic parts with a wide range of powders. However, a model, which can appropriately describe the shear rate dependence behavior of the slurry in casting process simulation, is limited. Therefore, this study mainly sought to investigate the best model representing the behavior of as-prepared gelcast slurry. A premix solution was prepared with monomer/cross linker of AM/MBAM with ratio of 25:1. In this procedure, ammonium polyacrylate sodium (NHPANa) was used as the dispersant and the solid load included Al2O3/20 vol% ZrO2 powder mixture. Series of slurries... 

    Control of Blood Flow by Endothelial-Secreted Biochemicals NO, Ca2+ and Growth Factor VEGF: Numerical Simulation Using Lattice Boltzmann-Finite Difference Hybrid

    , M.Sc. Thesis Sharif University of Technology Asghanian, Alireza (Author) ; Firoozabadi, Bahar (Supervisor)
    Endothelial cells that cover the inner wall of blood cells and are sensitive to receiving mechanical signals play important role in regulating many vital activities of the human body especially the function of the cardiovascular system. One of the factors affecting the mechanical functions of these cells is the shear stress applied to them. Due to blood velocity increasing or decreasing the endothelial cells shear stress change and leads to some chemical reactions and finally releasing biochemical substances including Nitrogen-Monoxide and Calcium-ion. Nitrogen-Monoxide produced by endothelial cells by affecting the smooth muscle cells in the vessel wall causes dilating of the vessel wall,... 

    Modeling of wormhole propagation in carbonate rocks by use of in-situ-gelled acids

    , Article SPE Journal ; Volume 22, Issue 6 , 2017 , Pages 2032-2048 ; 1086055X (ISSN) Hosseinzadeh, B ; Bazargan, M ; Rostami, B ; Ayatollahi, S ; Sharif University of Technology
    Diversion in heterogeneous carbonate reservoirs plays the most important role to the success of acidizing. Without the use of diversion, more acid preferentially flows into the high-permeability region and leaves the low-permeability region underreacted. But a clear understanding of diverting agents, such as polymer-based in-situ-gelled acids, can help uniformly stimulate the near-wellbore region. In this paper, we correct the rheological model that was developed by Ratnakar et al. (2013) according to experimental data from Gomaa and Nasr-El-Din (2010b) by considering shear-rate effect in a two-scale continuum model. It is found that the rheology parameters and shear rate are influential... 

    Liquid segregation behavior of semi-solid AZ91 alloy during back extrusion test

    , Article Journal of Alloys and Compounds ; Volume 477, Issue 1-2 , 2009 , Pages 822-827 ; 09258388 (ISSN) Khosravani, A ; Aashuri, H ; Davami, P ; Narimannezhad, A ; Hadian, R ; Sharif University of Technology
    The present work is focused on the segregation behavior of semi-solid AZ91 magnesium alloy with Ca content. For this purpose a simple back extrusion test was used and the semi-solid billet was fabricated through a cooling slope. Different shear rates were obtained by variation in ram speed and extrusion ratio. Microstructures of the extruded samples were investigated and liquid segregation was described by Darcy's law. Homogeneity was improved by using higher shear rates, produced either by increasing plunger velocity or extrusion ratio, while at very high shear rates the air was entrapped inside the wall of the extruded sample. © 2008 Elsevier B.V. All rights reserved  

    Development of a saturation-based μ(I)-rheology for wet granular materials using discrete element method

    , Article Scientia Iranica ; Volume 28, Issue 5 B , 2021 , Pages 2719-2732 ; 10263098 (ISSN) Ghorbani, R ; Taghizadeh Manzari, M ; Hajilouy Benisi, A ; Sharif University of Technology
    Sharif University of Technology  2021
    The present study employs Discrete Element Method (DEM) to establish a rheological model that relates the apparent viscosity of a granular material to shear rate, normal stress, and water saturation. In addition, a theoretical model was developed to determine water distribution and water-induced forces between particles for different saturations. The resulting forces were embedded in a 3D shear cell as a numerical rheometer, and a wet specimen was sheared between two walls. A power law rheological model was then obtained as a function of inertia number and saturation. It was found that up to a critical saturation, the apparent viscosity increased with saturation that was higher than that of... 

    Investigation of rheological behaviour of 316L stainless steel-3 wt-%TiC powder injection moulding feedstock

    , Article Powder Metallurgy ; Volume 48, Issue 2 , 2005 , Pages 144-150 ; 00325899 (ISSN) Khakbiz, M ; Simchi, A ; Bagheri, R ; Sharif University of Technology
    The rheological behaviour of powder injection moulding feedstock comprising of 316L stainless steel and 3 wt-%TiC powders was studied using a capillary rheometer. The flowability and the sensitivity of viscosity to shear rate and temperature of the feedstock were investigated and compared with those of the binder system and the 316L SS PIM feedstock. The general rheological indexes were examined through relevant equations and the influence of TiC addition on the mouldability of the 316L SS feedstock was determined. It was found that all the feedstocks are basically pseudoplastic but the values of flow behaviour index n are influenced by the TiC addition, the solid volume fraction and the... 

    Experimental Investigation of Rock Wettability Effect on Carbonate Reservoir Matrix Acidizing

    , M.Sc. Thesis Sharif University of Technology Karimi, Masoud (Author) ; Ayatollahi, Shahaboddin (Supervisor) ; Masihi, Mohsen (Supervisor)
    Matrix acidizing operation is one of the popular methods of well stimulation in the oil and gas industry which is used to remove near wellbore damage, increase the permeability, hence improve the production rate from the formation. Hydrochloric acid is used in the carbonate reservoirs to remove formation damage and create wormhole deep in the rock. It has been shown that with the proper operating design, significant improvement in the production rate can be obtained. A successful acid operations involves the proper selection of the candidate wells, identify the type of formation damage, stimulation method selection, correct design acidizing scenario, implementation of the technique and... 

    An experimental investigation of silica nanoparticles effect on the rheological behavior of polyacrylamide solution to enhance heavy oil recovery

    , Article Petroleum Science and Technology ; Volume 31, Issue 5 , 2013 , Pages 500-508 ; 10916466 (ISSN) Maghzi, A ; Mohebbi, A ; Kharrat, R ; Ghazanfari, M. H ; Sharif University of Technology
    The use of polymer flooding as one of enhanced oil recovery methods has recently increased. The occurrence of high shear rates in reservoir and near well bore through perforation nozzles during polymer flooding cause shear degradation of polymers and therefore polymer viscosity has decreased. Rheological behavior of polymer solution in different conditions of oil reservoir is one of the key factors to develop use of polymer solutions. A few researches are available regarding improving rheological behavior of polymeric solution. In this study, to investigate the effect of nanoparticles on rheological behavior of polymer solutions two samples were prepared: polyacrylamide solution in water and... 

    Analytical investigation of boundary layer growth and swirl intensity decay rate in a pipe

    , Article Archive of Applied Mechanics ; Volume 81, Issue 4 , 2011 , Pages 489-501 ; 09391533 (ISSN) Maddahian, R ; Kebriaee, A ; Farhanieh, B ; Firoozabadi, B ; Sharif University of Technology
    In this research, the developing turbulent swirling flow in the entrance region of a pipe is investigated analytically by using the boundary layer integral method. The governing equations are integrated through the boundary layer and obtained differential equations are solved with forth-order Adams predictor-corrector method. The general tangential velocity is applied at the inlet region to consider both free and forced vortex velocity profiles. The comparison between present model and available experimental data demonstrates the capability of the model in predicting boundary layer parameters (e.g. boundary layer growth, shear rate and swirl intensity decay rate). Analytical results showed... 

    Synthesis and analysis of the properties of ferro-fluids

    , Article ICONN 2010 - Proceedings of the 2010 International Conference on Nanoscience and Nanotechnology, 22 February 2010 through 26 February 2010, Sydney, NSW ; 2010 , Pages 91-93 ; 9781424452620 (ISBN) Maleki Jirsaraei, N ; Ghane Motlagh, B ; Ghane Golmohamadi, F ; Ghane Motlagh, R ; Rouhani, S ; Sharif University of Technology
    We report the rheological properties of ferro-fluid (FF) containing iron oxide nano-particles. At first, a FF was synthesized by using chemical co-precipitaton[1]. The microstructure study using SEM revealed that the FF contained nano-particles with the mean particle size of 35nm. The XRD study revealed that we have well crystallized structures of magnetite; they appeared to be approximately single crystalline structures. The rheological results proved that the FF has non Newtonian behavior, it is a shear thinning fluid in all magnetic fields, Moreover, the magnetic field increases the viscosity in a definite shear rate due to the nano-particles agglomerations and formation of chain-like... 

    On the viscosity of composite suspensions of aluminum and ammonium perchlorate particles dispersed in hydroxyl terminated polybutadiene-New empirical model

    , Article Journal of Colloid and Interface Science ; Volume 299, Issue 2 , 2006 , Pages 962-971 ; 00219797 (ISSN) Arefinia, R ; Shojaei, A ; Sharif University of Technology
    The rheological properties of fuel suspensions with various solid loadings up to close their maximum packing fraction and suspending media having different viscosities are investigated using the rotational viscometer at relatively low shear rates in which suspensions behave as Newtonian fluids. Aluminum (Al) and ammonium perchlorate (AP) particles are major solid components of any solid fuel system which should be distributed uniformly inside a polymeric binder based on hydroxyl terminated polybutadiene (HTPB). The experimental data generated in this investigation indicates that the relative viscosity of the suspensions is independent of viscosity of polymer binder, but in addition to solid... 

    A mechanistic understanding of the water-in-heavy oil emulsion viscosity variation: effect of asphaltene and wax migration

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 608 , 2021 ; 09277757 (ISSN) Piroozian, A ; Hemmati, M ; Safari, M ; Rahimi, A ; Rahmani, O ; Aminpour, S. M ; Beiranvand Pour, A ; Sharif University of Technology
    Elsevier B.V  2021
    The role of emulsions as a prevalent phenomenon is broadly investigated in the petroleum industry since forming the emulsion has many severe harmful implications. Heavy components of crude oil such as wax and asphaltene make the water-in-oil (w/o) emulsion more stable, while the role of these components on the emulsion viscosity has not been fully understood. In this regard, to find a proper demulsifier to break these emulsions, it is necessary to know the mechanisms of emulsion formation by heavy oil components. In this study, the effects of waxy-oil and asphaltenic-oil on w/o emulsion were investigated by measuring volume and viscosity of the formed emulsion after an elapsed time, followed... 

    Spinal muscle forces, internal loads and stability in standing under various postures and loads - Application of kinematics-based algorithm

    , Article European Spine Journal ; Volume 14, Issue 4 , 2005 , Pages 381-392 ; 09406719 (ISSN) Shirazi Adl, A ; El-Rich, M ; Pop, D. G ; Parnianpour, M ; Sharif University of Technology
    This work aimed to evaluate trunk muscle forces, internal loads and stability margin under some simulated standing postures, with and without external loads, using a nonlinear finite element model of the T1-S1 spine with realistic nonlinear load-displacement properties. A novel kinematics-based algorithm was applied that exploited a set of spinal sagittal rotations, initially calculated to minimize balancing moments, to solve the redundant active-passive system. The loads consisted of upper body gravity distributed along the spine with or without 200 N held in the hands, either in the front of the body or on the sides. Nonlinear and linear stability/perturbation analyses at deformed,... 

    An electroconductive, thermosensitive, and injectable chitosan/pluronic/gold-decorated cellulose nanofiber hydrogel as an efficient carrier for regeneration of cardiac tissue

    , Article Materials ; Volume 15, Issue 15 , 2022 ; 19961944 (ISSN) Tohidi, H ; Maleki Jirsaraei, N ; Simchi, A ; Mohandes, F ; Emami, Z ; Fassina, L ; Naro, F ; Conti, B ; Barbagallo, F ; Sharif University of Technology
    MDPI  2022
    Myocardial infarction is a major cause of death worldwide and remains a social and healthcare burden. Injectable hydrogels with the ability to locally deliver drugs or cells to the damaged area can revolutionize the treatment of heart diseases. Herein, we formulate a thermo-responsive and injectable hydrogel based on conjugated chitosan/poloxamers for cardiac repair. To tailor the mechanical properties and electrical signal transmission, gold nanoparticles (AuNPs) with an average diameter of 50 nm were physically bonded to oxidized bacterial nanocellulose fibers (OBC) and added to the thermosensitive hydrogel at the ratio of 1% w/v. The prepared hydrogels have a porous structure with open... 

    Thermophysical and rheological behavior of polystyrene/silica nanocomposites: Investigation of nanoparticle content

    , Article Materials and Design ; Volume 32, Issue 8-9 , 2011 , Pages 4537-4542 ; 02641275 (ISSN) Vaziri, H. S ; Omaraei, I.A ; Abadyan, M ; Mortezaei, M ; Yousefi, N ; Sharif University of Technology
    In this work, solvent blending in combination with extruding are applied to provide polystyrene/silica nanocomposite specimens. Transmission electron microscope (TEM) and scanning electron microscope (SEM) show same nanoparticle dispersion in PS matrix in low to high filler loadings. Differential scanning calorimetry (DSC), dynamic mechanical thermal analyzer (DMTA) and thermogravimetric analyzer (TGA) were used to study the thermophysical characteristic of the nanocomposites in solid state. In addition, the melt state rheological behavior of the samples was investigated under constant and zero shear rates. Interestingly, different behaviors were detected in nanocomposites in low and high... 

    CFD-DEM Model for Simulation of Non-spherical Particles in Hole Cleaning Process

    , Article Particulate Science and Technology ; Volume 33, Issue 5 , 2015 , Pages 472-481 ; 02726351 (ISSN) Akhshik, S ; Behzad, M ; Rajabi, M ; Sharif University of Technology
    Taylor and Francis Inc  2015
    During the well drilling process, particles are produced in different shapes. The shape of particles can influence the characteristics of particles transport process. The aim of this work is to analyze the effects of particle shape on the transportation mechanism. For this purpose, a three-dimensional model is prepared for simulation of particle transportation with spherical and non-spherical shapes, during deviated well drilling. The motion of particles and the non-Newtonian fluid flow are simulated via discrete element method and CFD, respectively. The two-way coupling scheme is used to incorporate the effects of fluid-particle interactions. Three different samples of non-spherical shapes... 

    Comparison of rheological behavior of branched polypropylene prepared by chemical modification and electron beam irradiation under air and N2

    , Article Radiation Physics and Chemistry ; Volume 79, Issue 10 , 2010 , Pages 1088-1094 ; 0969806X (ISSN) Mousavi, S. A ; Dadbin, S ; Frounchi, M ; Venerus, D. C ; Medina, T. G ; Sharif University of Technology
    Chemical and electron beam irradiation methods were used to introduce a branched structure into polypropylene and propylene-ethylene copolymer. The chemical method was carried out in an internal mixer using initiator and TMPTMA monomer. In irradiation method, the polymer was irradiated by electron beam under air and nitrogen atmosphere. The branched structure in the modified polymer was confirmed by rheological measurements. While degradation was significant in chemical method, branching occurred efficiently by irradiation under air. Small amount of ethylene in the propylene copolymer promoted branching over degradation  

    Rheology and colloidal structure of silver nanoparticles dispersed in diethylene glycol

    , Article Powder Technology ; Volume 197, Issue 1-2 , 2010 , Pages 49-53 ; 00325910 (ISSN) Tamjid, E ; Guenther, B. H ; Sharif University of Technology
    Rheological behavior of agglomerated silver nanoparticles (~ 40 nm) suspended in diethylene glycol over a wide range of volumetric solids concentrations (φ{symbol} = 0.11-4.38%) was studied. The nanoparticle suspensions generally exhibited a yield pseudoplastic behavior. Bingham plastic, Herschel-Bulkley and Casson models were used to evaluate the shear stress-shear rate dependency. Analyzing the effect of silver concentrations on the yield stress and viscosity of the suspensions followed an exponential form, revealing an increase in the degree of interparticle interactions with increasing solid concentrations. Fractal dimension (Df) was estimated from the suspension yield stress and... 

    Silane functionalization of nanodiamond for polymer nanocomposites-effect of degree of silanization

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 506 , 2016 , Pages 254-263 ; 09277757 (ISSN) Hajiali, F ; Shojaei, A ; Sharif University of Technology
    Elsevier B.V  2016
    The silanization of nanodiamond (ND) was successfully carried out by using the esterification reaction of hydrolyzed vinyltrimethoxysilane (VTS) in alcoholic solution. The surface carboxylic group of ND was first enhanced by thermal oxidation to increase the degree of esterification reaction. The extent of silane functionalization of ND was controlled by varying the weight ratio of VTS and oxidized ND (oxND), from 2:1 to 10:1 (w/w) in the functionalization reaction medium. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) revealed that the highest degree of silanization occurred at VTS/oxND of 5:1 (w/w), while more silane concentrations resulted in... 

    Diffuse emissions of particles from iron ore piles by wind erosion

    , Article Environmental Engineering Science ; Volume 28, Issue 5 , 2011 , Pages 333-339 ; 10928758 (ISSN) Afshar Mohajer, N ; Torkian, A ; Sharif University of Technology
    Industrial air pollution from point and nonpoint sources of steel complexes has drawn increasingly more public attention in the past decades. Previous research efforts have been more concentrated on point sources of particulate emissions from these complexes. However, wind-induced particulate emissions from iron ore storage piles not only result in ambient air pollution but also increase economic adverse effects to the industry by loss of process raw materials. Experiments were conducted to assess the impact of wind speed and humidity on particulate emission rates from iron ore storage piles. A wind-generating system and specific iron ore, experimental piles (L:W:H of 30:11.5:5 cm) were...