Search for: numerical-methods
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    Development of a consistent slip boundary condition at the inlet of microchannels

    , Article 44th AIAA Aerospace Sciences Meeting 2006, Reno, NV, 9 January 2006 through 12 January 2006 ; Volume 10 , 2006 , Pages 7087-7096 ; 1563478072 (ISBN); 9781563478079 (ISBN) Darbandi, M ; Vakilipour, S ; Schneider, G. E ; Sharif University of Technology
    The fast progress in Microelectromechanical systems has drawn the attention of many numerical workers to provide sufficient numerical tools to analyze the micro flows accurately. Besides many ambiguities behind the slip boundary condition research which are normally encountered in the vicinity of the solid walls (and are necessary to provide the suitable bridge between the macro and micro behaviors), there are serious uncertainties at the inlet of channels where the microflow enters into the conduit. Indeed, the macro inlet flow have been long investigated by the past workers; however, there is little effort to clarify the issue in micro inlet flow cases. In this research, we utilize the... 

    Developing a model for a two-echelon two-item inventory system with lost sale and demand substitution

    , Article 2006 IEEE International Conference on Management of Innovation and Technology, ICMIT 2006, Singapore, 21 June 2006 through 23 June 2006 ; Volume 2 , 2006 , Pages 926-930 ; 1424401488 (ISBN); 9781424401482 (ISBN) Akbari Jokar, M. R ; Zangeneh, S ; Sharif University of Technology
    Almost all multi-echelon inventory models assume that demands which are not satisfied immediately can be backordered. In some situations, this assumption may not be realistic. For example, we can model stockouts as lost sales when the retailers are in a competitive market and customers can easily turn to another retailer for purchasing goods. So, in this study, assuming lost sales at the retailers, we consider a one-warehouse, several retailers, two-item inventory system where the items can be interchangeably used. Using the well-known METRIC-approximation as a framework, we present a heuristic for finding cost effective base-stock policies. In a numerical study with simulation, we find that... 

    Computational aspects of the cosserat finite element analysis of localization phenomena

    , Article Computational Materials Science ; Volume 38, Issue 2 , 2006 , Pages 303-315 ; 09270256 (ISSN) Sharbati, E ; Naghdabadi, R ; Sharif University of Technology
    The computational aspects of the finite element solution procedure based on the Cosserat theory are studied for some elastic-plastic problems, in which the localization occurs. For this purpose, the equations of the Cosserat elasto-plasticity, which include effects of couple stress, micro-rotation and length scale, are presented. The Cosserat finite element formulation is derived and an algorithm for the solution procedure is proposed. For the elastic-plastic problems considered here, the mesh-independency of the Cosserat-based results is quantified and effects of the internal length and Cosserat material parameter a are investigated on the results. Also, the influence of the internal length... 

    Data association for multi-target elliptic localization in distributed MIMO radars

    , Article IEEE Communications Letters ; Volume 25, Issue 9 , 2021 , Pages 2904-2907 ; 10897798 (ISSN) Kazemi, S. A. R ; Amiri, R ; Behnia, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    In this letter, an efficient method for solving the multi-target localization problem in distributed MIMO radars is proposed. The proposed method attempts to simultaneously carry out the localization and data association tasks by formulating a mixed-integer optimization problem, which is approximated as a convex problem that can be efficiently solved with a polynomial complexity. Numerical simulations substantiate the efficacy of the proposed method. © 1997-2012 IEEE  

    A novel approach to coordination of large-scale systems; Part I - Interaction prediction principle

    , Article 2005 IEEE International Conference on Industrial Technology, ICIT 2005, Hong Kong, 14 December 2005 through 17 December 2005 ; Volume 2005 , 2005 , Pages 641-647 ; 0780394844 (ISBN); 9780780394841 (ISBN) Sadati, N ; Sharif University of Technology
    Coordination strategies in large-scale systems are mainly based on two principles; Interaction Prediction Principle and Interaction Balance Principle. In this paper, which consists of two parts, the concept of coordination is introduced within the framework of two-level large-scale systems, and two new approaches for coordination based on Interaction Prediction Principle and Interaction Balance Principle have been presented. The new strategies have much faster convergence rate than the previously suggested classical methods. They extremely reduce the number of iterations required for obtaining the overall optimal solutions. The efficacy and advantage of the proposed approaches, in compare to... 

    A combination of genetic algorithm and simulated annealing for optimal DG allocation in distribution networks

    , Article Canadian Conference on Electrical and Computer Engineering 2005, Saskatoon, SK, 1 May 2005 through 4 May 2005 ; Volume 2005 , 2005 , Pages 645-648 ; 08407789 (ISSN) Gandomkar, M ; Vakilian, M ; Ehsan, M ; Sharif University of Technology
    This paper presents a new algorithm based on integrating the use of genetic algorithms and simulated annealing methods to optimal allocation of distributed generation resources in distribution networks. Through this algorithm a significant improvement in the optimization goal is achieved. With a numerical example the superiority of the proposed algorithm is demonstrated in comparison with the simple genetic algorithm. © 2005 IEEE  

    Analytical approach for analyzing tapered transmission lines

    , Article 2005 European Conference on Circuit Theory and Design, Cork, 28 August 2005 through 2 September 2005 ; Volume 3 , 2005 , Pages 181-184 ; 0780390660 (ISBN); 9780780390669 (ISBN) Faraji, B ; Eghlidi, M. H ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
    A new analytical method is introduced for the analysis of wave propagation in one-dimensional tapered transmission lines. Based on the analytical extension of ordinary transfer matrix into differential transfer matrix, this approach can be used for calculating reflection and transmission coefficients. Different numerical test cases are thoroughly studied and in each case an excellent agreement between the results of our differential transfer matrix method and exact solutions is observed. It is also shown that our approach is superior to the more common small reflection method  

    Chaos synchronization using sliding mode technique

    , Article Wec 05: Fourth World Enformatika Conference, Istanbul, 24 June 2005 through 26 June 2005 ; Volume 6 , 2005 , Pages 159-162 ; 9759845857 (ISBN); 9789759845858 (ISBN) Khademian, B ; Haeri, M ; Sharif University of Technology
    In this paper, an effective sliding mode design is applied to chaos synchronization. The proposed controller can make the states of two identical modified Chua's circuits globally asymptotically synchronized. Numerical results are provided to show the effectiveness and robustness of the proposed method. COPYRIGHT © ENFORMATIKA  

    Efficient polynomial root finding using SIMD extensions

    , Article 11th International Conference on Parallel and Distributed Systems Workshops, ICPADS 2005, Fukuoka, 20 July 2005 through 22 July 2005 ; Volume 2 , 2005 , Pages 529-533 ; 15219097 (ISSN); 0769522815 (ISBN) Moslemi, M ; Ahmadi, H ; Sarbazi Azad, H ; Ma J ; Yang L. T ; Sharif University of Technology
    In this paper, the parallel implementations of different iterative polynomial root finding methods on a processor with SIMD processing capability are reported. These methods are based on the construction of a sequence of approximations that converge to the set of roots. We have chosen four widely used methods namely Newton's, Durand-Kerner's, Aberth-Ehrlich's, and QD and implemented them using the SIMD instruction set of the Pentium processor with C++ and assembly language. Experiments show that a speedup of 3 or higher can be achieved, depending on the order of polynomial, required accuracy, and the method employed. © 2005 IEEE  

    Finite volume discretization of flow in porous media by the MATLAB system

    , Article Scientia Iranica ; Volume 11, Issue 1-2 , 2004 , Pages 146-152 ; 10263098 (ISSN) Shamsai, A ; Vosoughifar, H. R ; Sharif University of Technology
    Sharif University of Technology  2004
    In this paper, a finite volume scheme is used to discretize flow in porous media. A numerical method for treating advection-dominated contaminant transport for flow of groundwater is described. This system combines the advantages of numerical discretization and the finite volume method (like local mass conservation). The equations are dicretized using a finite volume approach. The resulting nonlinear differential system is integrated in time using a solver. The conservation of energy (convection-diffusion) equation is solved using a special method for reducing the oscillation induced by the standard finite volume method. Consequently, a mathematical model for multi-component flow transport... 

    Dynamics modeling of "Cedra" rescue robot on uneven terrains

    , Article 2004 ASME International Mechanical Engineering Congress and Exposition, IMECE, Anaheim, CA, 13 November 2004 through 19 November 2004 ; Volume 73, Issue 2 PART B , 2004 , Pages 991-1001 Meghdari, A ; Mahboobi, S. H ; Gaskarimahalle, A. L ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2004
    In this paper an effective approach for kinematic and dynamic modeling of high mobility wheeled mobile robots (WMR) has been presented. As an example of these robots, the method has been applied on CEDRA rescue robot which is a complex, multibody mechanism. The model is derived for 6-DOF motions enabling movement in x, y, z directions, as well as pitch, roll and yaw rotations. Forward kinematics equations are derived using Denavit-Hartenberg method and the wheels Jacobian matrices. Moreover the inverse kinematics of the robot is obtained and solved for the wheel velocities and steering commands in terms of desired velocity, heading and measured link angles. Finally dynamical analysis of the... 

    Effects of confining walls on laminar natural convection from a horizontal cylinder

    , Article Proceedings of the Intersociety Energy Conversion Engineering Conference ; Volume 2 , 2000 , Pages 1261-1267 ; 0146955X (ISSN) Sadeghipour, M. S ; Razi, Y. P ; Sharif University of Technology
    The laminar natural convection from an isothermal horizontal cylinder confined between vertical walls is investigated by experimental and numerical methods. The experimental and numerical data are well correlated, independently, to equations which give the average Nusselt number in terms of the wall spacing to cylinder diameter ratio, t/D, and the Rayleigh number, Ra, for two different values of the wall height to cylinder diameter ratios, H/D=7 and 15.2. For the low Rayleigh numbers considered (Ra<1000), there are certain conditions for the confining walls under which heat transfer from the cylinder is maximum. Results are compared with the reported numerical and/or experimental results... 

    Assessment of Performance Based Behavior of of the Rock Mass Abutment Anchorage System during Construction of Karun IV Bridge by Numerical Methods

    , M.Sc. Thesis Sharif University of Technology Ghorbanzadeh, Alireza (Author) ; Sadaghiani, Mohammad Hossein (Supervisor)
    Three dimensional analyses have been carried out for predicting the behavior of the jointed rock slope of the abutments of the bridge which is proposed to be constructed across the river Karun4 in Iran using 3DEC. The rock overall slope angle is approximately 60 to 70 degrees, composed of highly jointed rock mass and the joint spacing and orientation are varying at different locations. Since 3DEC is a three-dimensional numerical code, utilizes a Lagrangian calculation scheme to model large movements and deformations of a blocky system, allows for modeling of large movements and rotations, and including complete detachment of rigid or deformable discrete blocks has been utilized for the... 

    Numerical Methods for Approximation and Visualization of Invariant Manifolds in Dynamical Systems

    , M.Sc. Thesis Sharif University of Technology Naderi Yeganeh, Hamid (Author) ; Razvan, Mohammad Reza (Supervisor)
    Invariant manifolds are important objects in the theory of dynamical systems. The stable manifold theorem is a very important theorem about this concept which proves the existence of stable and unstable manifolds in a wide range of dynamical systems. The importance of invariant manifolds encourages us to view their pictures. It helps us to understand their bahavior. For this purpose, at first we need to approximate the invariant manifold we want to visualize. There are several algorithms designed to approximate invariant manifolds. Those algorithms approximate a set of points on an invariant manifold and then provide an approximation of the manifold by the calculated points. Visualizing an... 

    Developing an Object-oriented Computer Program for Seepage Analysis through Earth Dams using Boundary Element Method

    , M.Sc. Thesis Sharif University of Technology Asadi, Roza (Author) ; Ashtiani, Ataie (Supervisor)
    Destruction of a dam is not only an economic disaster but also a catastrophe for the down stream residents. Seepage related problems are the main reasons for the destruction of the embankment dams. Therefore controlling seepage in an earth dam is of great importance.Graphical, experimental,and numerical methods can be applied for analysis of seepage problems in embankment dams.Due to the complexity of geometry and of in homogeneous and/or anisotropic media there are few analytical solutions to porous media problems. Numerical solutions have long played an important role in ground water calculation such as Finite Difference Method (FDM),Finite Element Method (FEM) and Boundary Element Method... 

    Measuring Limb Darkening of Distant Stars Using Microlensing Events by Finite Element Method

    , Ph.D. Dissertation Sharif University of Technology Golchin, Laya (Author) ; Rahvar, Sohrab (Supervisor)
    The finite-size effect in gravitational microlensing provides a possibility to measure the variation of surface brightness of stars from centre to limb which is called limb darkening profile. Measuring limb darkening profile provides information about star atmosphere. It is also useful in other fields of astrophysics. In this thesis we develop a numerical method to recover limb darkening of source stars from single lens microlensing light curves with finite source effect in which the lens transits the source disk. We use the Finite Element Method (FEM) as an inversion tool for discretization and inversion of the finite source effect integral equation. This method makes no explicit assumption... 

    Solving High-Dimensional Differential Equations Using Machine Learning

    , M.Sc. Thesis Sharif University of Technology Saffarieh, Pooya (Author) ; Razvan, Mohammad Reza (Supervisor) ; Moghadasi, Reza (Co-Supervisor)
    The numerical solution of differential equations in high dimensions has always been a challenge and has been associated with various computational difficulties. These equations appear naturally in a variety of problems such as financial mathematics, control, and physics, and their optimal solution with high accuracy and speed can open new windows on new applications. Conventional methods such as Finite element and finite difference method in high dimensions lose their efficiency, which is a barrier to fast and accurate calculation of these equations. In this dissertation first, we review some theoretical and practical aspects of deep neural networks and then we try to examine the recent... 

    Numerical Investigation of Off-axis translocation, Shape, and the Electrical Charge of a Nanoparticle in the Nanofluidic Conduit

    , M.Sc. Thesis Sharif University of Technology Jodeyri, Zohreh (Author) ; Taghipoor, Mojtaba (Supervisor)
    The advent of nanopore-based sensors based on resitive pulse sensing gave rise to a remarkable breakthrough in the detection and characterization of nanoscale species. The sensors can detect the species’concentration, size, and charge using the resistive pulse characteristics. Some strong correlations have been reported between the resitive pulse characteristics and the particle’s geometrical and physical properties. These correlations are commonly used to obtain information about the particles in commercial devices and research setups. The correlations, however, do not consider the simultaneous effect of influential factors such as particle shape, charge, and off-axis translocation, which... 

    Integrating load reduction into wholesale energy market with application to wind power integration

    , Article IEEE Systems Journal ; Vol. 6, issue. 1 , 2012 , p. 35-45 ; ISSN: 19328184 Parvania, M ; Fotuhi-Firuzabad, M ; Sharif University of Technology
    Renewable energy resources, notably wind power, are expected to provide considerable portion of the world energy requirements in the near future. Many system operators around the world are challenged by the problems associated with integrating these intermittent resources into the grid. As one of the potential solutions, demand response (DR) is expected to play a major role for mitigating integration issues of intermittent renewable energy resources. In this context, this paper proposes a DR program which helps to integrate wind power by reshaping the load of the system. The DR program provides a framework to procure load reduction from DR resources in the wholesale energy market. The... 

    Improved S2 approximations

    , Article Annals of Nuclear Energy ; Vol. 77 , 2014 , Pages 257-264 ; ISSN: 03064549 Safari, M. J ; Bahrami, M ; Sharif University of Technology
    Discrete ordinates method relies on approximating the integral term of the transport equation with the aid of quadrature summation rules. These quadratures are usually based on certain assumptions which assure specific symmetry rules and transport/diffusion limits. Generally, these assumptions are not problem-dependent which results in inaccuracies in some instances. Here, various methods have been developed for more accurate estimation of the independent angle in S2 approximation, as it is tightly related to valid estimation of the diffusion coefficient/length. We proposed and examined a method to reduce a complicated problem that usually is consisting many energy groups and discrete...