Search for: finite-difference-methods
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    Neural implant stimulation based on TiO2 nanostructured arrays; A multiphysics modeling verification

    , Article IECBES 2014, Conference Proceedings - 2014 IEEE Conference on Biomedical Engineering and Sciences: "Miri, Where Engineering in Medicine and Biology and Humanity Meet", 8 December 2014 through 10 December 2014 ; December , 2015 , Pages 677-680 ; 9781479940844 (ISBN) Sasanpour, P ; Mohammadpour, R ; Amiri, K ; Silterra; University of Malaya ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Exploiting of the nanostructure arrays as a promising candidate for excitation of neural cells has been analyzed. Based on the importance of the coupling effect between electrode and neuron, a multiphyscis modeling approach has been proposed. The model incorporates theoretically both structural effects (size, geometry) and electrophysiological effects. The system of equations for proposed model has been solved numerically using Finite Element Method for Poisson equation and Finite Difference Method for Cable equation. In this regards we have combined the system of equations in COMSOL platform with Matlab interface accordingly. We have analyzed the effect of excitation of neuron with an extra... 

    Active vibration control of a cmos-mems nano-newton capacitive force sensor for bio application using PZT

    , Article Advanced Materials Research, San Diego, CA ; Volume 628 , 2013 , Pages 317-323 ; 10226680 (ISSN) ; 9783037855706 (ISBN) Mozhdehi, R. J ; Selkghafari, A ; Zabiholah, A ; Meghdari, A ; Sharif University of Technology
    This paper reports the design of an optimal controller to prevent suppressvertical vibration due to undesired out of plane excitations generated by environment or gripper during manipulation for a CMOS-MEMS Nano-Newton capacitive force sensor applied for biomedical applications. Undesired out of plane excitations generated by environment or gripper during manipulation is the most prevalent source of vertical vibration in this type of sensors. To suppress the vibrational movement a PZT 5A is used as actuation mechanism. Discrete element method DEM model and Modal analysis were used to find dominant natural frequencies and mode shape vectors. To eliminate out of plane excitation an optimal... 

    Enhancement of full-duplex efficiency in an asymmetric IEEE 802.11-based WLAN

    , Article IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, 4 September 2016 through 8 September 2016 ; 2016 ; 9781509032549 (ISBN) Goshtasbpour, S ; Ashtiani, F ; Mirmohseni, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    In this paper, we propose a new packet prioritization scheme in order to exploit the full-duplex (FD) capability of the access point (AP) more efficiently, in an asymmetric IEEE 802.11-based WLAN, i.e., only the AP has the in-band FD communications capability. In this respect, we consider a modified version of IEEE 802.11 MAC protocol such that at any transmission opportunity in which AP has the role of the transmitter or the receiver, it does the best to select a partner packet to be simultaneously received or transmitted, respectively. The key feature of our proposed partner packet selection scheme is to reduce the idle time intervals that in an FD transmission opportunity, due to... 

    New insight into H2S sensing mechanism of continuous SnO2-CuO bilayer thin film: A theoretical macroscopic approach

    , Article Journal of Physical Chemistry C ; Volume 120, Issue 14 , 2016 , Pages 7678-7684 ; 19327447 (ISSN) Boroun, Z ; Ghorbani, M ; Moosavi, A ; Mohammadpour, R ; Sharif University of Technology
    American Chemical Society  2016
    SnO2-CuO is one the most promising systems for detection of detrimental H2S gas. Although previous experimental research has suggested a sulfidation reaction to explain selectivity toward H2S, little is known about the origin of change of electrical response of this system by changing the H2S gas concentration. In this study the relation between sensing response of continuous SnO2-CuO bilayer thin film and H2S gas concentration is computed based on changeability of chemical composition of covellite CuxS. For this purpose, chemical activity of sulfur as a function of atomic fraction in covellite copper sulfide is estimated using Gibbs energies of formation and chemical thermodynamics. By... 

    Effects of viscoelastic supports on the behavior of bridges under moving vehicles

    , Article Scientia Iranica ; Volume 24, Issue 4 , 2017 , Pages 1751-1769 ; 10263098 (ISSN) Samanipour, K ; Vafai, H ; Sharif University of Technology
    Sharif University of Technology  2017
    One of the most important problems facing structural engineers is the analysis of dynamic behavior of bridges subjected to moving vehicles. In addition, viscoelastic supports under bridges change their dynamic behavior under passing traffic loads. This paper presents how to model a bridge with viscoelastic supports and how the maximum dynamic stress of bridges changes during the passing of moving vehicles. Furthermore, this paper presents an algorithm to solve the governing equation of the bridge with viscoelastic supports as well as the equation of motion of a real European truck with different speeds, simultaneously. Using viscoelastic supports with appropriate characteristics can make a... 

    Assessment of characteristic boundary conditions based on the artificial compressibility method in generalized curvilinear coordinates for solution of the Euler equations

    , Article Computational Methods in Applied Mathematics ; Volume 18, Issue 4 , 2018 , Pages 717-740 ; 16094840 (ISSN) Parseh, K ; Hejranfar, K ; Sharif University of Technology
    De Gruyter  2018
    The characteristic boundary conditions are applied and assessed for the solution of incompressible inviscid flows. The two-dimensional incompressible Euler equations based on the artificial compressibility method are considered and then the characteristic boundary conditions are formulated in the generalized curvilinear coordinates and implemented on both the far-field and wall boundaries. A fourth-order compact finite-difference scheme is used to discretize the resulting system of equations. The solution methodology adopted is more suitable for this assessment because the Euler equations and the high-accurate numerical scheme applied are quite sensitive to the treatment of boundary... 

    Delayed data offloading based on full-duplex D2D communications in a cellular network

    , Article 2018 Iran Workshop on Communication and Information Theory, IWCIT 2018, 25 April 2018 through 26 April 2018 ; 2018 , Pages 1-6 ; 9781538641491 (ISBN) Karami, F ; Mirmohseni, M ; Ashtiani, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    In this paper, we propose a new delayed data offloading scheme by exploiting full-duplex (FD) device-to-device (D2D) communications. To this end, we consider a scenario in which a common file is requested by a subset of users in different times and with different maximum tolerable delays. Moreover, a maximum specific bandwidth is dedicated for data transmission. In order to send the file in the specific bandwidth, we use multicasting alongside FD D2D communications. Thanks to the fact that users have different deadlines, we divide them into non-overlapping groups, i.e., coalitions, to receive the file in distinct intervals. In order to guarantee the tolerable delay of all users, a coalition... 

    Analytical investigation of composite sandwich beams filled with shape memory polymer corrugated core

    , Article Meccanica ; Volume 54, Issue 10 , 2019 , Pages 1647-1661 ; 00256455 (ISSN) Akbari Azar, S ; Baghani, M ; Zakerzadeh, M. R ; Shahsavari, H ; Sohrabpour, S ; Sharif University of Technology
    Springer Netherlands  2019
    Shape memory polymers (SMPs) are a class of smart materials which can recover their shape even after many shape changes in application of an external stimulus. In this paper, flexural behavior of a composite beam, constructed of a corrugated part filled with SMPs, is studied. This composite beam is applicable in sensor and actuator applications. Since the corrugated profiles display higher stiffness-to-mass ratio in the transverse to the corrugation direction, the beams with a corrugated part along the transverse direction are stiffer than ones with a corrugated part along the length. Employing a developed constitutive model for SMPs and the Euler–Bernoulli beam theory, the behavior of the... 

    Secrecy performance of friendly jammer assisted cooperative NOMA systems with internal eavesdroppers

    , Article 31st IEEE Annual International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2020, 31 August 2020 through 3 September 2020 ; Volume 2020-August , 2020 Abolpour, M ; Aissa, S ; Mirmohseni, M ; Aref, M. R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    In non-orthogonal multiple access (NOMA) systems, serving multiple users in shared resource blocks can allow untrusted users to overhear the messages of other users. In this context, we study a network consisting of a base station (BS), a near user and a far user, where the latter attempts to overhear the message of the former. The near user is a full-duplex (FD) node that can also act as a relay. Two operating scenarios are considered: 1) friendly jammer (FJ), where the FD node broadcasts noise for degrading the channel between the BS and the far user, while receiving data from the BS; and 2) friendly jammer relay (FJR), where, in addition to degrading the channel between the BS and the far... 

    Delay-Optimal cooperation policy in a slotted aloha full-duplex wireless network: static approach

    , Article IEEE Systems Journal ; Volume 14, Issue 2 , 2020 , Pages 2257-2268 Vaezi, K ; Ashtiani, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    We consider a cooperative wireless communication network comprising two full-duplex (FD) nodes transmitting to a common destination based on slotted Aloha protocol. Each node has exogenous arrivals and also may relay some of the unsuccessfully transmitted packets of the other node. In this article, we find the optimal static policies of nodes in order to minimize the sum of the average transmission delays, while the average transmission delay of each node is constrained. The static policy of each node specifies the probability of accepting an unsuccessfully transmitted packet of the other node and how the node prioritizes its transmissions. We show that in the optimal policies, just the node... 

    The application of corrugated parallel bundle model to immobilized cells in porous microcapsule membranes

    , Article Journal of Membrane Science ; Volume 311, Issue 1-2 , 2008 , Pages 159-164 ; 03767388 (ISSN) Biria, D ; Zarrabi, A ; Khosravi, A ; Sharif University of Technology
    To describe immobilized cells in porous microcapsule membranes with straight pores, a novel model called corrugated parallel bundle model (CPBM) was utilized. In this model, a network was developed with 10 main pores each composing 10 pore elements. Cell growth kinetic in the network was examined using non-structural models. Effectiveness factor and pore plugging time were calculated by solving reaction-diffusion equation set via finite difference method. The findings revealed that diffusion coefficient for lower order reactions will create a lesser impact on the reduction of effectiveness factor. These findings also indicated that the use of such supporting carrier for cell immobilization... 

    A new parallel Gauss-Seidel method based on alternating group explicit method and domain decomposition method

    , Article Applied Mathematics and Computation ; Volume 188, Issue 1 , 2007 , Pages 713-719 ; 00963003 (ISSN) Tavakoli, R ; Davami, P ; Sharif University of Technology
    A new parallel Gauss-Seidel method is presented for solution of system of linear equations related to finite difference discretization of partial differential equations. This method is based on domain decomposition method and local coupling between interfaces of neighbor sub-domains, same as alternating group explicit method. This method is convergent and number of iterations for achieving convergence criteria is near the original Gauss-Seidel method (sometimes better and sometimes worse but difference is very small). The convergence theory is discussed in details. Numerical results are given to justify the convergence and performance of the proposed iterative method. © 2006 Elsevier Inc.... 

    A higher-order Boussinesq-type model with moving bottom boundary: Applications to submarine landslide tsunami waves

    , Article International Journal for Numerical Methods in Fluids ; Volume 53, Issue 6 , 2007 , Pages 1019-1048 ; 02712091 (ISSN) Ataie Ashtiani, B ; Najafi Jilani, A ; Sharif University of Technology
    A two-dimensional depth-integrated numerical model is developed using a fourth-order Boussinesq approximation for an arbitrary time-variable bottom boundary and is applied for submarine-landslide-generated waves. The mathematical formulation of model is an extension of (4,4) Padé approximant for moving bottom boundary. The mathematical formulations are derived based on a higher-order perturbation analysis using the expanded form of velocity components. A sixth-order multi-step finite difference method is applied for spatial discretization and a sixth-order Runge-Kutta method is applied for temporal discretization of the higher-order depth-integrated governing equations and boundary... 

    Implementation of high-order compact schemes to the iterative parabolized Navier-Stokes equations

    , Article 25th Congress of the International Council of the Aeronautical Sciences 2006, Hamburg, 3 September 2006 through 8 September 2006 ; Volume 3 , 2006 , Pages 1628-1643 Esfahanian, V ; Hejranfar, K ; Darian, H. M ; Sharif University of Technology
    Curran Associates Inc  2006
    The numerical solution of the parabolized Navier-Stokes (PNS) and globally iterated PNS (IPNS) equations for accurate computation of hypersonic axisymmetric flowfields is obtained by using the fourth-order compact finite-difference method. The PNS and IPNS equations in the general curvilinear coordinates are solved by using the implicit finite-difference algorithm of Beam and Warming type with a high-order compact accuracy. A shock fitting procedure is utilized in both the compact PNS and IPNS schemes to obtain accurate solutions in the vicinity of the shock. The main advantage of the present formulation is that the basic flow variables and their first and second derivatives are... 

    BEM modeling of surface water wave motion with laminar boundary layers

    , Article Engineering Analysis with Boundary Elements ; Volume 30, Issue 1 , 2006 , Pages 14-21 ; 09557997 (ISSN) Jamali, M ; Sharif University of Technology
    This study is concerned with numerical modeling of viscous surface wave motion using boundary element method (BEM). The equations of motion for thin boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to obtain the viscosity-related quantities such as wave damping rate, shear stress, and velocity distribution inside the boundary layer. The technique is presented for standing surface wave motion. An excellent agreement is obtained between the numerical predictions and the previous results. The extension to other free surface problems is straightforward. © 2005 Elsevier Ltd. All rights reserved  

    Numerical simulation of liquid/gas phase flow during mold filling

    , Article Computer Methods in Applied Mechanics and Engineering ; Volume 196, Issue 1-3 , 2006 , Pages 697-713 ; 00457825 (ISSN) Tavakoli, R ; Babaei, R ; Varahram, N ; Davami, P ; Sharif University of Technology
    A numerical model for simulation of liquid/gas phase flow during mold filling is presented. The incompressible Navier-Stokes equations are discretized on a fixed Cartesian mesh with finite difference method. The fractional-step scheme is employed for enforcing incompressibility constraint. The free surface effects are calculated using the volume of fluid method based on the piecewise-linear interface reconstruction and split Lagrangian advection of volume fraction field. Adding limited compressibility to the gas phase led to improvement in convergence rate of Poisson equation solver (about 2-fold). This new concept permits simulation of two-phase incompressible free surface flow during mold... 

    An approximated solution to the 2D incompressible Navier-Stokes equations via Adomian Decomposition Method

    , Article WSEAS Transactions on Mathematics ; Volume 5, Issue 7 , 2006 , Pages 878-885 ; 11092769 (ISSN) Najafi, M ; Taeibi Rahni, M ; Aavani, K ; Sharif University of Technology
    The Adomian Decomposition Method (ADM) for solving the highly non-linear vorticity-stream function formulation of 2D incompressible Navier-Stokes equations has been implemented. The analysis is accompanied by numerical boundary conditions. Also, numerical simulation, using finite difference method (FDM), is performed for comparison purposes. The obtained results only for few terms of the expansion are presented. Because present software such as Mathematica/Maple can not calculate many terms (for example: up to 10 terms) of solution and then ADM approach of this problem is an open problem case  

    A study on mutual interaction between atomistic and macroscopic phenomena during electrochemical processes using FD-KMC model: Application to CV test in simple copper sulfate bath

    , Article Journal of Electroanalytical Chemistry ; Volume 592, Issue 1 , 2006 , Pages 95-102 ; 15726657 (ISSN) Saedi, A ; Sharif University of Technology
    Elsevier  2006
    A multiscale FD-KMC model has been developed to simulate the cyclic voltammetry test of a copper electrode in simple copper sulfate bath. In this coupled model, the FD code provides the cupric ion concentration on OHP for KMC code, while the KMC code provides the electrochemical properties of the copper electrode (surface activity and rate constants of redox reactions) as an input data for FD code. The changes in the electrode properties due to the atomistic phenomena (deposition dissolution and surface diffusion) have been studied for the present potentiodynamic system. The results showed that the CV process consists of some distinct stages, so that the electrode exhibits a specific... 

    A coupled boundary element-finite difference model of surface wave motion over a wall turbulent flow

    , Article International Journal for Numerical Methods in Fluids ; Volume 51, Issue 4 , 2006 , Pages 371-383 ; 02712091 (ISSN) Jamali, M ; Sharif University of Technology
    An effective numerical technique is presented to model turbulent motion of a standing surface wave in a tank. The equations of motion for turbulent boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to model the wave motion and the corresponding boundary layer flow. A mixing-length theory is used for turbulence modelling. The model results are in good agreement with previous physical and numerical experiments. Although the technique is presented for a standing surface wave, it can be easily applied to other free surface problems. Copyright © 2005 John Wiley & Sons, Ltd  

    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...