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    Assessment of steady and unsteady flamelet models for MILD combustion modeling

    , Article International Journal of Hydrogen Energy ; Volume 43, Issue 32 , 2018 , Pages 15551-15563 ; 03603199 (ISSN) Chitgarha, F ; Mardani, A ; Sharif University of Technology
    Moderate or intense low-oxygen dilution (MILD) combustion is a novel combustion technology with the comparable chemical and turbulent mixing timescales. In the most of literatures, relatively expensive volume-based models are recommended for this combustion regime while this regime is not completely idealized homogenized reactor and nor strong flamelet like. This paper is focused on the assessment of the lower cost, flamelet approach for MILD condition. In this way, simplifying JHC burner of Dally et al. is considered to model using RANS approach. The effects of inclusion of unity versus non-unity Lewis numbers, radiation heat transfer, and various scalar dissipation rates are evaluated.... 

    Model reference adaptive impedance control in Cartesian coordinates for physical human-robot interaction

    , Article Advanced Robotics ; Vol. 28, issue. 19 , October , 2014 , pp. 1277-1290 ; ISSN: 01691864 Sharifi, M ; Behzadipour, S ; Vossough, G. R ; Sharif University of Technology
    In this paper, a nonlinear model reference adaptive impedance controller is proposed and tested. The controller provides asymptotic tracking of a reference impedance model for the robot end-effector in Cartesian coordinates applicable to rehabilitation robotics or any other human-robot interactions such as haptic systems. The controller uses the parameters of a desired stable reference model which is the target impedance for the robots end-effector. It also considers uncertainties in the model parameters of the robot. The asymptotic tracking is proven using Lyapunov stability theorem. Moreover, the adaptation law is proposed in joint space for reducing the complexity of its calculations;... 

    On the modeling of the static recrystallization considering the initial grain size effects

    , Article Materials Science and Engineering A ; Volume 486, Issue 1-2 , 2008 , Pages 202-207 ; 09215093 (ISSN) Kazeminezhad, M ; Sharif University of Technology
    Modeling of the static recrystallization in deformed copper specimens with different initial grain sizes is carried out based on a previous dislocation-grain size interaction model and a Monte Carlo simulation. From the dislocation-grain size interaction model, the stored energy of the deformed copper is calculated considering the interaction of the dislocations due to the different initial grain sizes. Then, utilizing the stored energy and Monte Carlo simulation the kinetic of recrystallization and recrystallized grain sizes are obtained. The JMAK plots of the modeling results show that, in conditions of 2D modeling and site-saturated nucleation, the Avrami exponent is 2 ± 0.1. The time for... 

    Network Design and Hub Location Problems with the Dependency of Demands

    , M.Sc. Thesis Sharif University of Technology Foroughi, Amir (Author) ; Akbari Jokar, Mohammad Reza (Supervisor)
    The hub networks are applied for commodity flows in the systems, among whose nodes the direct connections are both impossible and expensive. The dependency and interaction of demands are dealt with in this thesis. The dependency of demands are the results of some significant aspects, the most important of which are selecting or not selecting a node as a station, allocating or not allocating a demand to a hub, and associating with a path, to name but a few. Then, the ideas of hub location problem, interaction model, and eventually commodity transportation have been considered together.
    In this master thesis, a model having a quadratic and non-linear objective function has been developed.... 

    Presumed Joint-PDF modelling for turbulent stratified flames

    , Article Flow, Turbulence and Combustion ; Volume 107, Issue 2 , 2021 , Pages 405-439 ; 13866184 (ISSN) Ghadimi, M ; Atayizadeh, H ; Salehi, M. M ; Sharif University of Technology
    Springer Science and Business Media B.V  2021
    Turbulence–chemistry interaction models such as the conditional moment closure and various flamelet models require a presumed Probability Density Function (PDF) model of the conditioning variables. In turbulent stratified flames, a joint-PDF model for a reaction progress variable and the mixture fraction is required. The joint-PDF is often modelled by two beta functions using the first and second moments of the two conditioning variables. In this work, the performance of a joint-PDF model based on the flamelet PDF approach is compared to the double beta-PDF model. The conditional PDF of the reaction progress variable conditioned on mixture fraction is modelled with the flamelet PDF. Unlike... 

    A dynamic fuzzy interactive approach for DG expansion planning

    , Article International Journal of Electrical Power and Energy Systems ; Volume 43, Issue 1 , 2012 , Pages 1094-1105 ; 01420615 (ISSN) Esmi Jahromi, M ; Ehsan, M ; Fattahi Meyabadi, A ; Sharif University of Technology
    This paper presents a dynamic multi objective model for distribution network expansion, considering the distributed generators (DGs) and network reinforcements. The proposed model simultaneously optimizes three objective functions namely, total cost, emission cost and technical satisfaction (voltage profile) by finding the optimal schemes of timing, sizing, placement and DG technologies in a long term planning period (dynamic planning). The importance of each objective function can be changed in the interactive steps. The calculation algorithm is based on Chaotic Local Search with Modified Honey Bee Mating Optimization (CLSMHBMO). The effectiveness of the proposed model and the calculation... 

    Nonlinear multivariable modeling and stability analysis of vibrations in horizontal drill string

    , Article Applied Mathematical Modelling ; Volume 71 , 2019 , Pages 525-542 ; 0307904X (ISSN) Salehi, M. M ; Moradi, H ; Sharif University of Technology
    Elsevier Inc  2019
    Nowadays, economical extraction of the oil and gas, and their products is an important problem. Up to now, vertical wells have been used for oil extraction but some wells exist that they cannot be reached by using the vertical drilling. Horizontal and directional drillings are some techniques to reach these wells. In this article, dynamics of the horizontal drill string is studied. According to the forces that affect the dynamics of drilling, its longitudinal vibration is analyzed. After determination of the boundary conditions and normal modes of the system with using mode summation method, displacement of the bit is obtained. Finally, dynamics of the horizontal drill string is simulated... 

    Predicting the solubility of SrSO4 in Na-Ca-Mg-Sr-Cl-SO4-H2O system at elevated temperatures and pressures

    , Article Fluid Phase Equilibria ; Vol. 374, issue , July , 2014 , p. 86-101 ; ISSN: 03783812 Safari, H ; Shokrollahi, A ; Moslemizadeh, A ; Jamialahmadi, M ; Ghazanfari, M. H ; Sharif University of Technology
    Precipitation of strontium sulfate (or SrSO4) has already been distinguished as one of the most costly and critical problems which may occur in process industries and oilfield operations. Costs due to scaling and remedial actions that need to be taken afterward are generally high owing to low solubility of SrSO4 in aqueous solutions. Therefore, a thorough understanding of the SrSO4 thermodynamic behavior under various operating conditions is vital to predict or even avoid the overall damage caused by scaling. The primary aim of this work is to develop a model based on Least Squares Support Vector Machine (LSSVM) and Coupled Simulated Annealing (CSA) referred to as CSA-LSSVM to predict... 

    Analyses of mass and heat transport interactions in a direct methanol fuel cell

    , Article International Journal of Hydrogen Energy ; Vol. 39, issue. 21 , July , 2014 , p. 11224-11240 ; ISSN: 03603199 Kalantari, H ; Baghalha, M ; Sharif University of Technology
    In this paper, a two-dimensional, two-phase, non-isothermal model is presented to predict the electrochemical, mass transfer and heat transfer behaviors in a direct methanol fuel cell (DMFC). Governing equations including the momentum, continuity, heat transfer, proton and electron transport, species transport for water, methanol, and all the gas species (carbon dioxide, methanol vapor, water vapor, oxygen, and nitrogen) and the auxiliary equations are coupled to studying the various phenomena in DMFC. The modeling results agree well with the four different experimental data in an extensive range of operation conditions. A parametric study is also performed to examine the effects of the cell... 

    2D computational fluid dynamic modeling of human ventricle system based on fluid-solid interaction and pulsatile flow

    , Article Basic and Clinical Neuroscience ; Volume 4, Issue 1 , 2013 , Pages 64-75 ; 2008126X (ISSN) Masoumi, N ; Framanzad, F ; Zamanian, B ; Seddighi, A. S ; Moosavi, M. H ; Najarian, S ; Bastani, D ; Sharif University of Technology
    Many diseases are related to cerebrospinal fluid (CSF) hydrodynamics. Therefore, understanding the hydrodynamics of CSF flow and intracranial pressure is helpful for obtaining deeper knowledge of pathological processes and providing better treatments. Furthermore, engineering a reliable computational method is promising approach for fabricating in vitro models which is essential for inventing generic medicines. A Fluid-Solid Interaction (FSI)model was constructed to simulate CSF flow. An important problem in modeling the CSF flow is the diastolic back flow. In this article, using both rigid and flexible conditions for ventricular system allowed us to evaluate the effect of surrounding brain... 

    Discrete bubble model for prediction of bubble behavior in 3D fluidized beds

    , Article Chemical Engineering and Technology ; Volume 35, Issue 5 , 2012 , Pages 929-936 ; 09307516 (ISSN) Movahedirad, S ; Ghafari, M ; Dehkordi, A. M ; Sharif University of Technology
    A discrete bubble model has been developed taking into account multiple bubble-bubble interactions and a delayed coalescence method. The obtained simulation results were compared with experimental data reported in literature. The simulation results predicted by the developed model indicate clearly that the multiple interactions of bubbles lead to more reasonable results than those predicted by a binary interaction model. In addition, two types of interaction models were applied and predicted results were compared. The frequency of gas bubbles passing through the bed cross section versus bed height follows the same trend as the experimental data. A new modified discrete bubble model has been... 

    Design of integral abutment bridges for combined thermal and seismic loads

    , Article Earthquake and Structures ; Volume 9, Issue 2 , 2015 , Pages 415-430 ; 20927614 (ISSN) Easazadeh Far, N ; Maleki, S ; Barghian, M ; Sharif University of Technology
    Techno Press  2015
    Integral abutment bridges have many advantages over bridges with expansion joints in terms of economy and maintenance costs. However, in the design of abutments of integral bridges temperature loads play a crucial role. In addition, seismic loads are readily transferred to the substructure and affect the design of these components significantly. Currently, the European and American bridge design codes consider these two load cases separately in their recommended design load combinations. In this paper, the importance and necessity of combining the thermal and seismic loads is investigated for integral bridges. A 2D finite element combined pile-soil-structure interactive model is used in this...