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    On hyperbolic clifford algebras with involution

    , Article Algebra Colloquium ; Volume 20, Issue 2 , 2013 , Pages 251-260 ; 10053867 (ISSN) Mahmoudi, M. G ; Sharif University of Technology
    2013
    Abstract
    The aim of this article is to provide a characterization of quadratic forms of low dimension such that the canonical involutions of their Clifford algebras are hyperbolic  

    Hybridizing harmony search algorithm with sequential quadratic programming for engineering optimization problems

    , Article Computer Methods in Applied Mechanics and Engineering ; Volume 197, Issue 33-40 , 2008 , Pages 3080-3091 ; 00457825 (ISSN) Fesanghary, M ; Mahdavi, M ; Minary Jolandan, M ; Alizadeh, Y ; Sharif University of Technology
    2008
    Abstract
    This study presents a hybrid harmony search algorithm (HHSA) to solve engineering optimization problems with continuous design variables. Although the harmony search algorithm (HSA) has proven its ability of finding near global regions within a reasonable time, it is comparatively inefficient in performing local search. In this study sequential quadratic programming (SQP) is employed to speed up local search and improve precision of the HSA solutions. Moreover, an empirical study is performed in order to determine the impact of various parameters of the HSA on convergence behavior. Various benchmark engineering optimization problems are used to illustrate the effectiveness and robustness of... 

    Solving fuzzy quadratic programming problems based on ABS algorithm

    , Article Soft Computing ; Volume 23, Issue 22 , 2019 , Pages 11343-11349 ; 14327643 (ISSN) Ghanbari, R ; Ghorbani Moghadam, K ; Sharif University of Technology
    Springer Verlag  2019
    Abstract
    Recently, Ghanbari and Mahdavi-Amiri (Appl Math Model 34:3363–3375, 2010) gave the general compromised solution of an LR fuzzy linear system using ABS algorithm. Here, using this general solution, we solve quadratic programming problems with fuzzy LR variables. We convert fuzzy quadratic programming problem to a crisp quadratic problem by using general solution of fuzzy linear system. By using this method, the crisp optimization problem has fewer variables in comparison with other methods, specially when rank of the coefficient matrix is full. Thus, solving the fuzzy quadratic programming problem by using our proposed method is computationally easier than the solving fuzzy quadratic... 

    A new inexact nonmonotone filter sequential quadratic programming algorithm

    , Article 5th International Conference on Numerical Analysis and Optimization: Theory, Methods, Applications and Technology Transfer, NAOV 2020, 6 January 2020 through 9 January 2020 ; Volume 354 , 2021 , Pages 1-24 ; 21941009 (ISSN); 9783030720391 (ISBN) Ahmadzadeh, H ; Mahdavi Amiri, N ; Sharif University of Technology
    Springer  2021
    Abstract
    An inexact nonmonotone filter sequential quadratic programming algorithm is presented for solving general constrained nonlinear programming problems. At every iteration, a steering direction is computed as a minimizer of a linear model of the constraint violation over a trust region. A possible infeasible stationary point can be detected using the steering direction. If the current iterate is not an infeasible stationary point, a strongly convex feasible quadratic programming subproblem is defined to compute a search direction as an inexact solution satisfying some loose and achievable conditions. We prove that the search direction is a descent direction for the constraint violation or the... 

    A new inexact nonmonotone filter sequential quadratic programming algorithm

    , Article 5th International Conference on Numerical Analysis and Optimization: Theory, Methods, Applications and Technology Transfer, NAOV 2020, 6 January 2020 through 9 January 2020 ; Volume 354 , 2021 , Pages 1-24 ; 21941009 (ISSN) ; 9783030720391 (ISBN) Ahmadzadeh, H ; Mahdavi Amiri, N ; Sharif University of Technology
    Springer  2021
    Abstract
    An inexact nonmonotone filter sequential quadratic programming algorithm is presented for solving general constrained nonlinear programming problems. At every iteration, a steering direction is computed as a minimizer of a linear model of the constraint violation over a trust region. A possible infeasible stationary point can be detected using the steering direction. If the current iterate is not an infeasible stationary point, a strongly convex feasible quadratic programming subproblem is defined to compute a search direction as an inexact solution satisfying some loose and achievable conditions. We prove that the search direction is a descent direction for the constraint violation or the... 

    Team selection for prediction tasks

    , Article Journal of Combinatorial Optimization ; 2014 ; ISSN: 15732886 Fazli, M ; Ghazimatin, A ; Habibi, J ; Haghshenas, H ; Sharif University of Technology
    Abstract
    Given a random variable (Formula presented.) and a set of experts (Formula presented.), we describe a method for finding a subset of experts (Formula presented.) whose aggregated opinion best predicts the outcome of (Formula presented.). Therefore, the problem can be regarded as a team formation for performing a prediction task. We show that in case of aggregating experts' opinions by simple averaging, finding the best team (the team with the lowest total error during past (Formula presented.) rounds) can be modeled with an integer quadratic programming and we prove its NP-hardness whereas its relaxation is solvable in polynomial time. At the end, we do an experimental comparison between... 

    Involutions of a clifford algebra induced by involutions of orthogonal group in characteristic 2

    , Article Communications in Algebra ; Volume 43, Issue 9 , Jun , 2015 , Pages 3898-3919 ; 00927872 (ISSN) Mahmoudi, M. G ; Nokhodkar, A. H ; Sharif University of Technology
    Taylor and Francis Inc  2015
    Abstract
    Among the involutions of a Clifford algebra, those induced by the involutions of the orthogonal group are the most natural ones. In this work, several basic properties of these involutions, such as the relations between their invariants, their occurrences, and their decompositions, are investigated  

    Duality in bipolar triangular fuzzy number quadratic programming problems

    , Article Proceedings of the International Conference on Intelligent Sustainable Systems, ICISS 2017, 7 December 2017 through 8 December 2017 ; 19 June , 2018 , Pages 1236-1238 ; 9781538619599 (ISBN) Ghorbani Moghadam, K ; Ghanbari, R ; Mahdavi Amiri, N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    We discuss how to solve bipolar fuzzy quadratic programming problems, where the parameters are bipolar triangular fuzzy numbers, making use of linear ranking functions. Also, we explore some duality properties of bipolar triangular fuzzy number quadratic programming problem (BTFNQPP). © 2017 IEEE  

    A variables neighborhood search algorithm for solving fuzzy quadratic programming problems using modified Kerre’s method

    , Article Soft Computing ; Volume 23, Issue 23 , 2019 , Pages 12305-12315 ; 14327643 (ISSN) Ghanbari, R ; Ghorbani Moghadam, K ; Mahdavi Amiri, N ; Sharif University of Technology
    Springer Verlag  2019
    Abstract
    To solve a fuzzy optimization problem, we need to compare fuzzy numbers. Here, we make use of our recently proposed modified Kerre’s method as an effective approach for comparison of LR fuzzy numbers. Using our new results on LR fuzzy numbers, we show that to compare two LR fuzzy numbers, we do not need to compute the fuzzy maximum of two numbers directly. We propose a new variable neighborhood search approach for solving fuzzy number quadratic programming problems by using the modified Kerre’s method. In our algorithm, a local search is performed using descent directions, found by solving five crisp mathematical programming problems. In several available methods, a fuzzy optimization... 

    A Truncated Sqp Method Based On Inexact Interior-Point Solutions Of Subproblems

    , M.Sc. Thesis Sharif University of Technology Bojari, Sanaz (Author) ; Mahdavi Amiri, Nezameddin (Supervisor)
    Abstract
    We consider sequential quadratic programming (SQP) methods applied to optimization problems with nonlinear equality constraints and simple bounds, recently introduced in the literature. In particular, we describe and analyze a truncated SQP algorithm due to Izmailov and Solodov in which subproblems are solved approximately by an infeasible predictor-corrector interior-point method, followed by setting to zero some variables and some multipliers so that complementarity conditions for approximate solutions are satisfied. Verifiable truncation conditions based on the residual of optimality conditions of subproblems are explained to ensure both global and fast local convergence. Global... 

    Traceability analysis of quadratic residue-based RFID authentication protocols

    , Article 2013 11th Annual Conference on Privacy, Security and Trust, PST 2013 ; 2013 , Pages 61-68 ; 9781467358392 (ISBN) Sohrabi Bonab, Z ; Alagheband, M. R ; Aref, M. R ; Sharif University of Technology
    2013
    Abstract
    Since low-cost RFID systems are applied in ubiquitous varied applications, privacy and security of their users became a great concern. Therefore, the various authentication protocols have been proposed. In this paper, we inspect the three new-found RFID authentication protocols based on quadratic residue property via one of the well-organized formal RFID privacy models instead of intuitive analysis. We formally prove that modular squaring is the suitable technique to guarantee RFID authentication protocols against backward traceability. Then, the flaws are alleviated to resist traceability attacks  

    The novel soliton solutions for the conformable perturbed nonlinear Schrödinger equation

    , Article Modern Physics Letters B ; Volume 36, Issue 8 , 2022 ; 02179849 (ISSN) Yépez-Martínez, H ; Pashrashid, A ; Gómez Aguilar, J. F ; Akinyemi, L ; Rezazadeh, H ; Sharif University of Technology
    World Scientific  2022
    Abstract
    The sub-equation method is implemented to construct exact solutions for the conformable perturbed nonlinear Schrödinger equation. In this paper, we consider three different types of nonlinear perturbations: The quadratic-cubic law, the quadratic-quartic-quintic law, and the cubic-quintic-septic law. The properties of the conformable derivative are discussed and applied with the help of a suitable wave transform that converts the governing model to a nonlinear ordinary differential equation. Furthermore, the order of the expected polynomial-type solution is obtained using the homogeneous balancing approach. Dark and singular soliton solutions are derived. © 2022 World Scientific Publishing... 

    Arithmetic Theory of Quadratic forms with Several Variables

    , M.Sc. Thesis Sharif University of Technology Mohammadi, Rasoul (Author) ; Jafari, Amir (Supervisor)
    Abstract
    In this thesis we review several arithmetical questions about the diophantine equation φ[x]=q where φ is a nondegenerate symmetric bilinear form on a finite dimensional vector space, φ[x] is the corresponding quadratic form and q is a nonzero element of the ground field. We obtain class number and mass formulae for the orthogonal group associated to φ in a number field utilizing the concept of quadratic forms, lattices and adelic language  

    The Number of Representations of an Integer by a Quadratic Form

    , M.Sc. Thesis Sharif University of Technology Khajehpour, Davood (Author) ; Pournaki, Mohammad Reza (Supervisor) ; Rajaei, Ali (Supervisor)
    Abstract
    In this paper Alexander Berkovich and Hamza Yesilyurt revisit old conjectures of Fermat and Euler regarding the representation of integers by binary quadratic form x2 + 5y2. Making use of Ramanujan’s 1 1 summation formula, they establish a new Lambert series identity for Σ1 n;m=1 qn2+5m2 . Conjectures of Fermat and Euler are shown to follow easily from this new formula. But they do not stop there. Employing various formulas found in Ramanujan’s notebooks and using a bit of ingenuity, they obtain a collection of new Lambert series for certain infinite products associated with quadratic forms such as x2+6y2, 2x2+3y2, x2+15y2, 3x2+5y2, x2+27y2, x2+5(y2+z2+w2), 5x2+y2+z2+w2. In the process, they... 

    Special classes of mathematical programming models with fuzzy random variables [electronic resource]

    , Article Journal of Intelligent and Fuzzy Systems, Published In: IOS Press ; Volume 19, Number 2, 2008 Eshghi, K. (Kourosh) ; Nematian, Javad ; Sharif University of Technology
    Abstract
    In this paper, we will discuss two special classes of mathematical programming models with fuzzy random variables. In the first model, a linear programming problem with fuzzy decision variables and fuzzy random coefficients is introduced. Then an algorithm is developed to solve the model based on fuzzy optimization method and fuzzy ranking method. In the second model, a fuzzy random quadratic spanning tree problem is presented. Then the proposed problem is formulated and solved by using the scalar expected value of fuzzy random variables. Furthermore, illustrative numerical examples are also given to clarify the methods discussed in this paper  

    Minimum norm solution of the absolute value equations via simulated annealing algorithm

    , Article Afrika Matematika ; Volume 26, Issue 7-8 , December , 2015 , Pages 1221-1228 ; 10129405 (ISSN) Moosaei, H ; Ketabchi, S ; Jafari, H ; Sharif University of Technology
    Springer Verlag  2015
    Abstract
    This paper mainly aims to obtain a minimum norm solution to the NP-hard absolute value equations (AVE) $$Ax-|x|=b$$Ax-|x|=b. In our proposed method, first we show that the AVE is equivalent to a bilinear programming problem and then we present a system tantamount to this problem. To find the minimum norm solution to the AVE, we solve a quadratic programming problem with quadratic and linear constraints. Eventually, we solve the obtained programming problem by Simulated Annealing algorithm. Numerical results support the efficiency of the proposed method and the high accuracy of calculation  

    On totally decomposable algebras with involution in characteristic two

    , Article Journal of Algebra ; Volume 451 , 2016 , Pages 208-231 ; 00218693 (ISSN) Gholamzadeh Mahmoudi, M ; Nokhodkar, A. H ; Sharif University of Technology
    Abstract
    A necessary and sufficient condition for a central simple algebra with involution over a field of characteristic two to be decomposable as a tensor product of quaternion algebras with involution, in terms of its Frobenius subalgebras, is given. It is also proved that a bilinear Pfister form, recently introduced by A. Dolphin, can classify totally decomposable central simple algebras of orthogonal type  

    Design a LQG power system stabilizer for bistun power plant

    , Article AUPEC'09 - 19th Australasian Universities Power Engineering Conference: Sustainable Energy Technologies and Systems, 27 September 2009 through 30 September 2009, Adelaide ; 2009 ; 9780863967184 (ISBN) Keivanian, R ; Hossein Vahabie, A ; Nademi, H ; Ranjbar, A ; Sharif University of Technology
    Abstract
    Design of a classical controller is based on output feedback and structure of the controller. From modern control point of view, the information of input signals, output signals and internal behavior of the system are presented in state space model. In this paper, modern control is used to increase small-disturbance stability of power systems. Although many of existing power plants prefer to use classical Power System Stabilizers (PSS), these controllers have their own problems. Digital implementation of modern controllers is considered as a good advantage of modern PSS. In this paper, a modern control based PSS is designed for Bistun power plant and its output results are compared to the... 

    A new method for the solution of hybrid analog digital beamforming problems

    , Article Optimal Control Applications and Methods ; Volume 41, Issue 5 , 2020 , Pages 1735-1748 Amini, E ; Reza Marzban, H ; Rastegari, M ; Sharif University of Technology
    John Wiley and Sons Ltd  2020
    Abstract
    By going to millimeter wave (mmWave) we can use large scale MIMO due to short mmWave wavelength to overcome path loss by using beamforming to focus power of signal to the receiver. System structure of mmWave band is different with conventional MIMO because of large scale MIMO which is leading to use many RF-chains. For this reason Hybrid structure have been proposed for large Scale MIMO. By going to Hybrid structure a new issue has been created with phase shifter constraint. In this paper we propose a novel solution to make a hybrid precoding and combing to reach high spectral efficiency. Our problem includes a maximizing Frobenius norm of multiplying five complex matrices. As constraints,... 

    Special classes of mathematical programming models with fuzzy random variables

    , Article Journal of Intelligent and Fuzzy Systems ; Volume 19, Issue 2 , 2008 , Pages 131-140 ; 10641246 (ISSN) Eshghi, K ; Nematian, J ; Sharif University of Technology
    2008
    Abstract
    In this paper, we will discuss two special classes of mathematical programming models with fuzzy random variables. In the first model, a linear programming problem with fuzzy decision variables and fuzzy random coefficients is introduced. Then an algorithm is developed to solve the model based on fuzzy optimization method and fuzzy ranking method. In the second model, a fuzzy random quadratic spanning tree problem is presented. Then the proposed problem is formulated and solved by using the scalar expected value of fuzzy random variables. Furthermore, illustrative numerical examples are also given to clarify the methods discussed in this paper