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    Enhancement of surface adsorption-desorption rates in microarrays invoking surface charge heterogeneity

    , Article Sensors and Actuators, B: Chemical ; 2016 ; 09254005 (ISSN) Abdollahzadeh, M ; Saidi, M. S ; Sadeghi, A ; Sharif University of Technology
    Elsevier B.V  2016
    Abstract
    This investigation is devoted to the influences of non-uniform wall characteristics on the surface adsorption-desorption rates in an electrokinetic microarray. Utilizing already explored electroosmotic and electrophoretic velocities, the species transport equations are solved by a finite-volume-based numerical approach. Uniform, sinusoidal, and pulse-like distributions of the zeta potential are considered in the analysis. The developed model is validated by comparing the results with those of two analytical solutions that are derived for limiting conditions. The results reveal that, in some cases, the surface charge heterogeneity can reduce the saturation time by more than 60%. The efficacy... 

    In situ horizontal stress from CPT in sand: a new approach

    , Article International Journal of Geotechnical Engineering ; 2017 , Pages 1-9 ; 19386362 (ISSN) Ahmadi, M. M ; Golestani Dariani, A. A ; Sharif University of Technology
    Abstract
    Despite the various approaches in the literature adopted for analysing cone penetration test (CPT), determination of the initial horizontal stress and relative density of a sandy soil during this test has not been tackled yet. In order to propose a new method in this regard, a numerical study of CPT has been performed and the predicted results have been compared with several databases of comprehensive calibration chamber tests. The penetration mechanism has been then fully investigated by presenting different kinds of outputs for the surrounding soil. Finally, an innovative procedure has been suggested for estimating the initial horizontal stress and relative density during performing CPT in... 

    3D modeling of reaction-diffusion dynamics in an electrokinetic Y-shaped microreactor

    , Article Sensors and Actuators, B: Chemical ; Volume 235 , 2016 , Pages 343-355 ; 09254005 (ISSN) Helisaz, H ; Saidi, M. H ; Sadeghi, A ; Sharif University of Technology
    Elsevier  2016
    Abstract
    We perform a 3D numerical modeling of reaction-diffusion dynamics in a Y-shaped microreactor, considering a fully developed combined electroosmotic and pressure-driven flow. The governing equations, based on a second-order irreversible reaction, are solved invoking a finite-volume approach for a non-uniform grid system. We demonstrate that the reaction is highly position dependent: more production is observed adjacent to the horizontal walls for a favorable pressure gradient, whereas both the wall and centerline are the regions of highest production when a back pressure is applied. We further show that, to achieve the maximum production rate, the EDL should be thick enough, the pressure... 

    Numerical and experimental investigations of weld pool geometry in GTA welding of pure aluminum

    , Article Journal of Central South University ; Vol. 21, issue. 1 , 2014 , p. 20-26 Faraji, A. H ; Bahmani, A ; Goodarzi, M ; Seyedein, S. H ; Shabani, M. O ; Sharif University of Technology
    Abstract
    A 2-D numerical model was developed to predict the shape of weld pool in stationary GTA welding of commercial pure aluminium, without considering fluid flow in the weld pool. A Gaussian current density and heat input distribution on the surface of the workpiece were considered. The parameters of Gaussian distribution were modified by comparing calculated results with experimental ones. It was found that these distribution parameters are functions of applied current and arc length. Effects of arc length, applied current and welding time on the geometry of the weld pool were investigated. To check the validity of the model, a series of experiments were also conducted. In general, the agreement... 

    Evaluation of behaviors of earth and rockfill dams during construction and initial impounding using instrumentation data and numerical modeling

    , Article Journal of Rock Mechanics and Geotechnical Engineering ; Volume 9, Issue 4 , 2017 , Pages 709-725 ; 16747755 (ISSN) Rashidi, M ; Haeri, S. M ; Sharif University of Technology
    Abstract
    In this study, the behavior of gavoshan dam was evaluated during construction and the first impounding. A two-dimensional (2D) numerical analysis was conducted based on a finite difference method on the largest cross-section of the dam using the results of instrument measurements and back analysis. These evaluations will be completed in the case that back analysis is carried out in order to control the degree of the accuracy and the level of confidence of the measured behavior since each of the measurements could be controlled by comparing it to the result obtained from the numerical model. Following that, by comparing the results of the numerical analysis with the measured values, it is... 

    In situ horizontal stress from CPT in sand: a new approach

    , Article International Journal of Geotechnical Engineering ; Volume 13, Issue 6 , 2019 , Pages 538-547 ; 19386362 (ISSN) Ahmadi, M. M ; Golestani Dariani, A. A ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    Despite the various approaches in the literature adopted for analysing cone penetration test (CPT), determination of the initial horizontal stress and relative density of a sandy soil during this test has not been tackled yet. In order to propose a new method in this regard, a numerical study of CPT has been performed and the predicted results have been compared with several databases of comprehensive calibration chamber tests. The penetration mechanism has been then fully investigated by presenting different kinds of outputs for the surrounding soil. Finally, an innovative procedure has been suggested for estimating the initial horizontal stress and relative density during performing CPT in... 

    Modeling the Flow and Infiltration of Surface Runoff in Swales

    , M.Sc. Thesis Sharif University of Technology Behrang, Koorosh (Author) ; Agha Mohammad Hossein Tajrishi, Massoud (Supervisor)
    Abstract
    Urbanization and increase in impervious areas owing to building construction, pavements of streets, parking lots and sidewalks, amount of surface runoff in cities has been rose. One of the environmental problems of Tehran during the rainfall is the high polluted runoff flowing in the city and eventually transfers pollution to aquifers. So in order to decline the consequences of this polluted surface runoff, it is crucial to understand how the runoff and pollution form. One way of decreasing pollution in runoff is hiring swales attenuation potential. In this study, problems associated with runoff, particularly in relation to the formation, transformation and removal of pollutants from runoff... 

    Modeling of Moisture-Induced Damage in Asphalt Mixtures

    , M.Sc. Thesis Sharif University of Technology Bozorgzad, Ashkan (Author) ; Tabatabaee, Nader (Supervisor)
    Abstract
    The deleterious effect of moisture on the structural integrity of asphalt mixtures has been recognized as one of the main causes of early deterioration of asphalt pavements. This phenomenon, usually referred to as moisture damage, is defined as the progressive loss of structural integrity of the mixture. Moisture damage is associated with the development of different physical, mechanical and chemical processes occurring within the microstructure of the mixture at different intensities and rates. Although there have been important advancements in identifying and characterizing this phenomenon, there is still a lack of understanding of the damage mechanisms occurring at the... 

    Analysis of Creep Behavior and Stability of Underground Fuel Storage in Rock Salt

    , M.Sc. Thesis Sharif University of Technology Narimani, Mohammad Ali (Author) ; Sadaghiani, Mohammadhosein (Supervisor)
    Abstract
    The purpose of this study is to analyze the stability and creeping behavior of rock salt in underground gas and oil reservoirs. Preparation of natural salt caverns and operating them can manipulate the initial state of previously existed stress and to produce deviatoric stresses around the cavern. New state of stress and with creeping behavior of rock salt, causes a significant decrease in cavern’s volume and damages the surrounding area. Reduction of internal minimum pressure of cavern, increases the intensity of mentioned problems. Geometrical characteristics of cavern can also be significantly effective in the magnitude of damages around the reservoir. For instance, Deflection of cavern... 

    Numerical Study of Geotextile Application in Downstream Filter Zone of an Embankment Dam with Clay Core

    , M.Sc. Thesis Sharif University of Technology Maghsoodian, Maedeh (Author) ; Shamsaie, Abolfazl (Supervisor)
    Abstract
    Nowadays, applications of the synthetic materials are developing in civil engineering projects and widely used in these projects. Therefore, during previous years; use of the Geotextiles as one of the Geosynthetic materials in order to filtration, drainage, separation, soil protection, etc have developed ever-increasing. The goal of this research is modeling and studies of the Geotextiles application in the downstream filter zone of embankment dams in combination with granular materials using FLAC2D software. Gordeh Bin embankment dam situated in West Azerbaijan province has been chosen as case study. In this matter, different models have been made with changes in thickness of the inclined... 

    Predictive tri-linear benchmark curve for in-plane behavior of adobe walls

    , Article International Journal of Architectural Heritage ; Volume 9, Issue 8 , Nov , 2015 , Pages 986-1004 ; 15583058 (ISSN) Rafsanjani, S. H ; Bakhshi, A ; Ghannad, M. A ; Yekrangnia, M ; Soumi, F ; Sharif University of Technology
    Taylor and Francis Inc  2015
    Abstract
    In the present study, numerical simulations are conducted to estimate the in-plane response of adobe walls subjected to pseudo-static cyclic loading based on the finite element code ABAQUS. The simplified micro-modeling approach is adopted and an interface model reported in ABAQUS material library is applied as material model for zero-thickness interface elements. The comparison between obtained results and field test data results in good agreement. Parametric studies are carried out to evaluate the effectiveness of independent parameters changes on response of adobe walls. It is noted that mechanical properties of joints and adobe units play an active role on in-plane behavior of walls. A... 

    A new approach for group efficiency of drilled shafts in sand subjected to axial loading

    , Article International Journal of Geotechnical Engineering ; 2016 , Pages 1-13 ; 19386362 (ISSN) Ahmadi, M. M ; Mahvelati, S ; Sharif University of Technology
    Taylor and Francis Ltd  2016
    Abstract
    Understanding pile group behaviour is a critical key for geotechnical engineers. Nevertheless, there have been inadequate studies in the literature which tackle the many aspects of this important type of foundation. In this paper, a new and simple approach is presented for estimating group efficiency of drilled shafts installed in sandy soil under axial loading. This approach may prove handy for geotechnical practitioners in their pile group design decisions. The distinguishing point about this approach is its being less-conservative in comparison with the rather few previous equations available in the literature. The mathematical approach derived in this study is based on results from... 

    A new approach for group efficiency of drilled shafts in sand subjected to axial loading

    , Article International Journal of Geotechnical Engineering ; Volume 12, Issue 2 , 2018 , Pages 172-184 ; 19386362 (ISSN) Ahmadi, M. M ; Mahvelati, S ; Sharif University of Technology
    Taylor and Francis Ltd  2018
    Abstract
    Understanding pile group behaviour is a critical key for geotechnical engineers. Nevertheless, there have been inadequate studies in the literature which tackle the many aspects of this important type of foundation. In this paper, a new and simple approach is presented for estimating group efficiency of drilled shafts installed in sandy soil under axial loading. This approach may prove handy for geotechnical practitioners in their pile group design decisions. The distinguishing point about this approach is its being less-conservative in comparison with the rather few previous equations available in the literature. The mathematical approach derived in this study is based on results from... 

    The 20–22 February 2016 mineral dust event in Tehran, Iran: numerical modeling, remote sensing, and In Situ measurements

    , Article Journal of Geophysical Research: Atmospheres ; Volume 123, Issue 10 , 27 May , 2018 , Pages 5038-5058 ; 2169897X (ISSN) Najafpour, N ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
    Blackwell Publishing Ltd  2018
    Abstract
    Wind erosion raises mineral dusts from dry and semidry lands and produces dust storms. Such dust masses have created numerous health and economic problems for the residents of southern, southwestern, and central parts of Iran. The main sources, movement, spread, and settlement of dust masses can be determined by solving the governing equations for aerosol transmission. Such information will be certainly useful in managerial decision-making. In this study, the dust event in Tehran on 20–22 February 2016 was studied using numerical model, Moderate Resolution Imaging Spectroradiometer satellite data, and data of ground-based stations. A comparison between the numerical results and in situ... 

    A numerical approach on side resistance of drilled shafts embedded in sandy soils

    , Article International Journal of Geotechnical Engineering ; 2019 ; 19386362 (ISSN) Jazebi, M ; Ahmadi, M. M ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    This study numerically investigates the side resistance of drilled shafts (bored piles) in sand using FLAC2D computer program. The results of the equations available in the literature are compared with the results of the present numerical study. A series of analyses is also conducted to assess the effects of various soil and pile parameters on the magnitude of side resistance of bored piles embedded in sand. Furthermore, the coupling (combined) effect of coefficient of lateral earth pressure with friction angle, and the coefficient of lateral earth pressure with a unit weight of soil on side resistance are investigated. The results show that the maximum effect of K0 on side resistance occurs... 

    Pore-scale investigation of selective plugging mechanism in immiscible two-phase flow using phase-field method

    , Article Oil and Gas Science and Technology ; Volume 74 , 2019 ; 12944475 (ISSN) Sabooniha, E ; Rokhforouz, M. R ; Ayatollahi, S ; Sharif University of Technology
    Editions Technip  2019
    Abstract
    The selective plugging effect of hydrophobic bacteria cell on secondary oil recovery performance was investigated. Water and aqua solution of purified Acinetobacter strain RAG-1 were injected into an oil-saturated heterogeneous micromodel porous media. Pure water injection expelled oil by 41%, while bacterial solution injection resulted in higher oil recovery efficiency (59%). In the simulation section, a smaller part of the heterogeneous geometry was applied as a computational domain. A numerical model was developed using coupled Cahn-Hilliard phase-field method and Navier-Stokes equations, solved by a finite element solver. In the non-plugging model, approximately 50% of the matrix oil was... 

    A numerical approach on side resistance of drilled shafts embedded in sandy soils

    , Article International Journal of Geotechnical Engineering ; 2019 ; 19386362 (ISSN) Jazebi, M ; Ahmadi, M. M ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    This study numerically investigates the side resistance of drilled shafts (bored piles) in sand using FLAC2D computer program. The results of the equations available in the literature are compared with the results of the present numerical study. A series of analyses is also conducted to assess the effects of various soil and pile parameters on the magnitude of side resistance of bored piles embedded in sand. Furthermore, the coupling (combined) effect of coefficient of lateral earth pressure with friction angle, and the coefficient of lateral earth pressure with a unit weight of soil on side resistance are investigated. The results show that the maximum effect of K0 on side resistance occurs... 

    3D numerical investigation of the effects of driving of the new mechanized tunnel on existing segmental linings and ground surface settlements - a case study: Shiraz metro line 2

    , Article International Journal of Geotechnical Engineering ; 2020 Pirastehfar, K ; Shivaei, S ; Sadaghiani, M. H ; Nikooee, E ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    Abstract
    Subway metro systems are one of the most efficient modes of mass transportation, especially in heavily populated areas. A series of 3D Finite Element Analysis (FEA) has been carried out to investigate the interaction between mechanized twin tunnels excavated beneath the highly congested streets of Shiraz (Iran). Firstly, the reference numerical model has been verified using the measured data of surface settlement control pins. The effects of driving of the new closed shield tunnel on the evolution of stress fields in the existing segmental lining as well as the ground surface settlements in the reference numerical model have been then quantified. Lastly, the effects of influencing factors... 

    Effect of EPB tunnelling on surface settlement

    , Article Annual Conference of the Canadian Society for Civil Engineering 2007: Where the Road Ends, Ingenuity Begins, Yellowknife, NT, 6 June 2007 through 9 June 2007 ; Volume 2 , 2007 , Pages 1003-1012 Sadaghiani, M. H ; Aliari, Y ; Sharif University of Technology
    2007
    Abstract
    Settlement is one of the most important effects of tunnelling. In order to minimize this effect, it is necessary to arrange for circumstances to keep the strain and stress state of undisturbed soil within a tight limit. To achieve this, it is common nowadays to use closed face pressurized shields such as EPB TBMs. In this type of shield, face stability and ground settlement control is maintained by pressurizing the tunnel face with adjustment of cutter head thrust and muck removal discharge. In this paper, numerical modeling of excavation of twin tunnels in Tabriz subway is addressed with respect to the effect of EPB tunnelling in settlement control. Settlement and lining thrust are... 

    A robust multi-objective optimization model for project scheduling considering risk and sustainable development criteria

    , Article Environment, Development and Sustainability ; Volume 23, Issue 8 , 2021 , Pages 11494-11524 ; 1387585X (ISSN) Askarifard, M ; Abbasianjahromi, H. R ; Sepehri, M ; Zeighami, E ; Sharif University of Technology
    Springer Science and Business Media B.V  2021
    Abstract
    There is limited research that considers the sustainability aspect of the projects’ schedule. The present study proposes a model to cover this gap by considering sustainable development criteria. A multi-objective model with four objective functions, including minimizing cost, risk, and socio-environmental impacts, has been presented to decrease the project’s delay. Since some of the parameters are considered under conditions of uncertainty for the proximity of problems to real projects, the robust programming method is used to deal with the uncertainty, and the epsilon-constraint method was applied to solve the multi-objective model. Several scenarios are also defined to analyze the...