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    Simple models of small-world networks with directed links

    , Article Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics ; Volume 66, Issue 3 , 2002 ; 1063651X (ISSN) Ramezanpour, A ; Karimipour, V ; Sharif University of Technology
    2002
    Abstract
    We investigate the effect of directed short- and long-range connections in a simple model of a small-world network. Our model is one in which we can determine many quantities of interest by an exact analytical method. We calculate the function [formula presented] defined as the number of sites affected up to time T when a naive spreading process starts in the network. As opposed to shortcuts, the presence of unfavorable bonds has a negative effect on this quantity. Hence, the spreading process may not be able to affect all of the network. We define and calculate a quantity identified as the average size of the accessible world in our model. The interplay of shortcuts and unfavorable bonds on... 

    New insight into hydrodynamic and cake erosion mechanism during rotating-disk dynamic microfiltration of concentrated bentonite suspensions at different salinity conditions

    , Article Separation and Purification Technology ; Volume 300 , 2022 ; 13835866 (ISSN) Movahedi, H ; Jamshidi, S ; Sharif University of Technology
    Elsevier B.V  2022
    Abstract
    The present study investigates the dynamic filtration of concentrated slurry fluids containing colloidal clay particles under different salinity, shear flow, and flux rate conditions. The dynamic filtration study was carried out by the filtration cell equipped with a rotating disk to apply shear stress over the membrane surface. A 3D CFD simulation has been implemented to model the hydrodynamic flows inside the filtration cell to obtain the wall shear stress (WSS) on the membrane surface at different disk rotation speeds. The thickness and surface patterns of fouling were captured utilizing a surface profilometer. First, the cake-filtration model was used to predict the flux rate and fouling... 

    Experimental and Theoretical Investigation on Entrainment Coefficient in Density Current and Introducing Modified Richardson Number

    , M.Sc. Thesis Sharif University of Technology Maleki Tehrani , Mahdi (Author) ; Firoozabadi, Bahar (Supervisor)
    Abstract
    Dense underflows are continuous currents, caused by interaction of two or more fluids of different density. Density currents move down-slope due their density being heavier than that of the ambient water. In this work, entrainment in 3-D density currents in a straight channel was investigated by a set of experimental studies and Theoretical calculations. Velocity components were measured using Acoustic Doppler Velocimetry (ADV). First of all, the bed shear stress was calculated by the velocity profile method and Reynolds stress method as well and showed a good agreement. By increasing the Richardson number, the bed shear stress decreases. On the other hand, the interface shear stress was... 

    Optimum arrangement of layers in multi-layer compound cylinders

    , Article International Journal of Applied Mechanics ; Vol. 6, issue. 5 , 2014 Sharifi, M ; Arghavani, J ; Hematiyan, M. R ; Sharif University of Technology
    Abstract
    In this paper, using an analytical optimization method, optimum design of multi-layer compound cylinders with different materials in layers is investigated. For this purpose, considering Tresca criterion, maximum shear stress in each layer is minimized. At the optimum condition, the maximum shear stress at all layers occurs simultaneously. The general analytical relations for optimum dimension of layers, residual pressures and radial interferences are derived. The existence condition of the optimum solution is also investigated and the constraints for materials selection are derived too. It is shown that the allowable shear stress ratio of materials must be close to their geometric mean... 

    Stress analysis in symmetric composite laminates subjected to shearing loads

    , Article International Journal of Mechanical Sciences ; Volume 75 , 2013 , Pages 16-25 ; 00207403 (ISSN) Mousanezhad viyand, D ; Yazdani Sarvestani, H ; Nosier, A ; Sharif University of Technology
    2013
    Abstract
    In the present study, an analytical solution is proposed to determine the interlaminar stresses in long symmetric laminated composite plates subjected to shearing loads. An improved first-order shear deformation theory (IFSDT) and a simplified IFSDT (SIFSDT) are utilized to calculate the unknown constants appearing in the reduced elasticity displacement field which actually demonstrate the global deformations of the plate. Then the numerical values of the interlaminar normal and shear stresses are established through the laminates by using Reddy's layerwise theory. Finally, several numerical examples are presented to study the interlaminar stresses in the interfaces of the layers and through... 

    Endothelial cells morphology in response to combined wss and biaxial cs: introduction of effective strain ratio

    , Article Cellular and Molecular Bioengineering ; Volume 13, Issue 6 , 2020 , Pages 647-657 Pakravan, H. A ; Saidi, M. S ; Firoozabadi, B ; Sharif University of Technology
    Springer  2020
    Abstract
    Introduction: Endothelial cells (ECs) morphology strongly depends on the imposed mechanical stimuli. These mechanical stimuli include wall shear stress (WSS) and biaxial cyclic stretches (CS). Under combined loading, the effect of CS is not as simple as pure CS. The present study investigates the morphological response of ECs to the realistic mechanical stimuli. Methods: The cell population is theoretically studied using our previous validated model. The mechanical stimuli on ECs are described using four parameters; WSS magnitude (0 to 2.0 Pa), WSS angle (− 50° to 50°), and biaxial CS in two perpendicular directions (0 to 10%). The morphology of ECs is reported using four parameters; average... 

    Effect of Stenotic Carotid Geometry on Flow and Stroke-risk

    , M.Sc. Thesis Sharif University of Technology Amirkhosravi, Mehrad (Author) ; Firoozabadi, Bahar (Supervisor) ; Saeedi, Saeed (Supervisor)
    Abstract
    Carotid bifurcation is one of the most important bifurcations in human body which has a lot of curvature in some people. The common carotid artery bifurcates into an internal carotid artery (ICA) and an external carotid artery (ECA). The incidence of stenosis in carotid bifurcation and in particular in the internal carotid artery is of special importance. In the United States of America by 2006, nearly 700000 strokes occur each year, with about 160000 deaths and 20 to 30% of strokes are caused by stenotic carotid that cost estimated at $160 billion. The purpose of this thesis is to investigate in hemodynamic factors of blood flow such as velocity variation, vortex patterns, shear stress and... 

    Remarks on numerical prediction of wall shear stress in entry flow problems

    , Article Communications in Numerical Methods in Engineering ; Volume 20, Issue 8 , 2004 , Pages 619-625 ; 10698299 (ISSN) Darbandi, M ; Hosseinizadeh, S. F ; Sharif University of Technology
    2004
    Abstract
    Today, commercial CFD codes are widely used to simulate many different entry flow problems. The flow in the developing zone undergoes a transition from a specified velocity profile at the inlet section to a fully developed profile in the region far from the inlet. Previous investigations have shown that the hydrodynamic variables, such as velocity and pressure magnitudes, along the centreline converge to a mesh independent solution even when coarse grid distributions are utilised. However, the present work shows that the local velocity profile is highly dependent on grid resolution in the vicinity of solid boundaries. It is shown that failure to account for the grid resolution can result in... 

    Implementation of Shear Stress in M-K Model for Determination of the Limit Strains

    , M.Sc. Thesis Sharif University of Technology Ghazanfari, Ahmad (Author) ; Asempour, Ahmad (Supervisor) ; Hashemi, Ramin (Co-Advisor)
    Abstract
    One of the most useful methods in metal forming is Sheet Metal Forming. Use of Forming limit diagrams (FLD) in designing is a conventional method. Therefore many experimental and theoretical efforts have been carried out in order to investigate the FLDs. Many ways to obtain this FLDs and their effective parameters have been studied. But the stress state at these studies is planar which lead to an untrue model for several metal forming process such as incremental sheet forming. With this technique, the forming limit curve (FLC) appears in a different pattern, revealing an enhanced formability, compared to conventional forming techniques. Therefore, in this study, the effect of through... 

    Evaluation of Shear Stress at the Interface of Asphalt Layers Using Finite Element Analysis

    , M.Sc. Thesis Sharif University of Technology Amjadyan, Yousef (Author) ; Tabatabaee, Nader (Supervisor)
    Abstract
    Tack coat is a layer of asphaltic materials, which is used for binding the surface layer to the current asphalt layer. The appropriate interlayer bonding condition will help different layers form a monolithic structure to resist traffic. The lack of proper interlayer bonding result in slippage between pavement layers, decrease the capability for transferring the load to the underlying layers, rutting, crescent cracking and decreasing the life of the Overlay. This study intends to model a pavement system in three dimensions with ABAQUS software in order to evaluate the amount of shear stress at the interface of asphalt layers. In order to prove the validity of the model, the results of the... 

    Investigation of wall shear stress related factors in realistic carotid bifurcation geometries and different flow conditions

    , Article Scientia Iranica ; Volume 17, Issue 5 B , 2010 , Pages 358-366 ; 10263098 (ISSN) Jamalian Ardakani, S. S ; Jafarnejad, M ; Firoozabadi, B ; Saidi, M. S ; Sharif University of Technology
    Abstract
    Cardiovascular diseases are one of the major causes of death in the world; atherosclerosis being one aspect. Carotid bifurcation is one of the sites that are vulnerable to this disease. Wall Shear Stress (WSS) is known to be responsible for the process of atherogenesis. In this study, we have simulated the blood flow for Newtonian and non-Newtonian, steady and unsteady, flow conditions in three idealistic and five realistic geometries. A risk factor has been presented based on the results of wall shear stress and, then, a relation was found between geometrical features and the wall shear stress risk factor. Our main conclusions are: 1) The non-Newtonian behavior of blood elevates the value... 

    The importance of fluid-structure interaction simulation for determining the mechanical stimuli of endothelial cells and atheroprone regions in a coronary bifurcation

    , Article Scientia Iranica ; Volume 23, Issue 1 , 2016 , Pages 228-237 ; 10263098 (ISSN) Pakravan, H. A ; Saidi, M. S ; Firoozabadi, B ; Sharif University of Technology
    Sharif University of Technology  2016
    Abstract
    The function and morphology of Endothelial Cells (ECs) play a key role in atherosclerosis. The mechanical stimuli of ECs, such as Wall Shear Stress (WSS) and arterial wall strain, greatly inuence the function and morphology of these cells. The present article deals with computations of these stimuli for a 3D model of a healthy coronary artery bifurcation. The focus of the study is to propose an accurate method for computations of WSS and strains. Two approaches are considered: Coupled simultaneous simulation of arterial wall and blood flow, called fluid-Structure Interaction (FSI) simulation, and decoupled, which simulates each domain (fluid and solid domain) separately. The study... 

    Entropy minimization in turbine cascade using continuous adjoint formulation

    , Article Engineering Optimization ; Volume 48, Issue 2 , 2016 , Pages 213-230 ; 0305215X (ISSN) Zeinalpour, M ; Mazaheri, K ; Sharif University of Technology
    Taylor and Francis Ltd 
    Abstract
    A complete continuous adjoint formulation is presented here for the optimization of the turbulent flow entropy generation rate through a turbine cascade. The adjoint method allows one to have many design variables, but still afford to compute the objective function gradient. The new adjoint system can be applied to different structured and unstructured grids as well as mixed subsonic and supersonic flows. For turbulent flow simulation, the k-ω shear-stress transport turbulence model and Roe's flux function are used. To ensure all possible shape models, a mesh-point method is used for design parameters, and an implicit smoothing function is implemented to avoid the generation of non-smoothed... 

    Simulation of low density lipoprotein (LDL) permeation into multilayer coronary arterial wall: interactive effects of wall shear stress and fluid-structure interaction in hypertension

    , Article Journal of Biomechanics ; 2017 ; 00219290 (ISSN) Roustaei, M ; Nikmaneshi, M. R ; Firoozabadi, B ; Sharif University of Technology
    Abstract
    Due to increased atherosclerosis-caused mortality, identification of its genesis and development is of great importance. Although, key factors of the origin of the disease is still unknown, it is widely believed that cholesterol particle penetration and accumulation in arterial wall is mainly responsible for further wall thickening and decreased rate of blood flow during a gradual progression. To date, various effective components are recognized whose simultaneous consideration would lead to a more accurate approximation of Low Density Lipoprotein (LDL) distribution within the wall. In this research, a multilayer Fluid-Structure Interaction (FSI) model is studied to simulate the penetration... 

    Performance analysis of elliptic-profile airfoil cascade for designing reversible axial flow fans

    , Article AIAA Journal ; Volume 57, Issue 4 , 2019 , Pages 1492-1501 ; 00011452 (ISSN) Abdolmaleki, M ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2019
    Abstract
    Because reversible fans must be able to provide similar performance in either rotation direction, they need to have completely symmetrical blades. In the present study, an elliptic profile with itsmaximum thickness of 8%chord length at themiddle of the chord line is studied. For verification, theNACA0012 airfoilwas once analyzed two-dimensionally in the isolatedformationandonce in cascade formation with0.55 and 0.83 solidities, andthe obtainedresultswere comparedwith numerical and experimental results. Three well-known Reynolds-averaged Navier-Stokes turbulence models including Spalart-Allmaras, realizable κ-ϵ, and shear-stress transport κ-ω were used to find the suitable turbulence method.... 

    Prediction of FLD for sheet metal by considering through-thickness shear stresses

    , Article Mechanics Based Design of Structures and Machines ; 2019 ; 15397734 (ISSN) Ghazanfari, A ; Soleimani, S. S ; Keshavarzzadeh, M ; Habibi, M ; Assempuor, A ; Hashemi, R ; Sharif University of Technology
    Taylor and Francis Inc  2019
    Abstract
    In this study, the effect of through-thickness shear (TTS) stress has been examined on the prediction of forming limit diagrams (FLDs). Determination of the FLD is based on the Marciniak–Kuczynski (M–K) model with some modifications on the stress states for consideration of the TTS stress effects. For solving the equations, the Newton–Raphson method has been used. Furthermore, the Nakazima test has been simulated to investigate the stress state which occurs in the sheet during the test. Results showed that the formability of sheet metal could be better as the through-thickness stress increased. Also, implementation of TTS stress in the present model, the corresponding FLD has better... 

    Performance analysis of elliptic-profile airfoil cascade for designing reversible axial flow fans

    , Article AIAA Journal ; Volume 57, Issue 4 , 2019 , Pages 1492-1501 ; 00011452 (ISSN) Abdolmaleki, M ; Afshin, H ; Farhanieh, B ; Sharif University of Technology
    American Institute of Aeronautics and Astronautics Inc  2019
    Abstract
    Because reversible fans must be able to provide similar performance in either rotation direction, they need to have completely symmetrical blades. In the present study, an elliptic profile with itsmaximum thickness of 8%chord length at themiddle of the chord line is studied. For verification, theNACA0012 airfoilwas once analyzed two-dimensionally in the isolatedformationandonce in cascade formation with0.55 and 0.83 solidities, andthe obtainedresultswere comparedwith numerical and experimental results. Three well-known Reynolds-averaged Navier-Stokes turbulence models including Spalart-Allmaras, realizable κ-ϵ, and shear-stress transport κ-ω were used to find the suitable turbulence method.... 

    Prediction of FLD for sheet metal by considering through-thickness shear stresses

    , Article Mechanics Based Design of Structures and Machines ; 2019 ; 15397734 (ISSN) Ghazanfari, A ; Soleimani, S. S ; Keshavarzzadeh, M ; Habibi, M ; Assempuor, A ; Hashemi, R ; Sharif University of Technology
    Taylor and Francis Inc  2019
    Abstract
    In this study, the effect of through-thickness shear (TTS) stress has been examined on the prediction of forming limit diagrams (FLDs). Determination of the FLD is based on the Marciniak–Kuczynski (M–K) model with some modifications on the stress states for consideration of the TTS stress effects. For solving the equations, the Newton–Raphson method has been used. Furthermore, the Nakazima test has been simulated to investigate the stress state which occurs in the sheet during the test. Results showed that the formability of sheet metal could be better as the through-thickness stress increased. Also, implementation of TTS stress in the present model, the corresponding FLD has better... 

    Prediction of FLD for sheet metal by considering through-thickness shear stresses

    , Article Mechanics Based Design of Structures and Machines ; Volume 48, Issue 6 , 2020 , Pages 755-772 Ghazanfari, A ; Soleimani, S. S ; Keshavarzzadeh, M ; Habibi, M ; Assempuor, A ; Hashemi, R ; Sharif University of Technology
    Taylor and Francis Inc  2020
    Abstract
    In this study, the effect of through-thickness shear (TTS) stress has been examined on the prediction of forming limit diagrams (FLDs). Determination of the FLD is based on the Marciniak–Kuczynski (M–K) model with some modifications on the stress states for consideration of the TTS stress effects. For solving the equations, the Newton–Raphson method has been used. Furthermore, the Nakazima test has been simulated to investigate the stress state which occurs in the sheet during the test. Results showed that the formability of sheet metal could be better as the through-thickness stress increased. Also, implementation of TTS stress in the present model, the corresponding FLD has better... 

    Rock joint modeling using a visco-plastic multilaminate model at constant normal load condition

    , Article Geotechnical and Geological Engineering ; Volume 24, Issue 5 , 2006 , Pages 1449-1468 ; 09603182 (ISSN) Mahin Roosta, R ; Sadaghiani, M. H ; Pak, A ; Saleh, Y ; Sharif University of Technology
    2006
    Abstract
    Rock joints play an important role in the behavior of rock masses under normal and shear loading conditions. Numerical simulation of the behavior of jointed rock masses is not an easy task due to complexities involved in the problem such as joint roughness, joint shear strength, hardening and softening phenomenon and mesh dependency. In this study for modeling purposes, a visco-plastic multilaminate model considering hardening and softening effects has been employed. For providing the necessary data for numerical simulation, a series of laboratory experiments have been carried out on regular tooth-shape asperities made by gypsum, under constant normal load conditions. Shear stress-shear...