Search for: linear-transformations
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    On linear transformations preserving at least one eigenvalue

    , Article Proceedings of the American Mathematical Society ; Volume 132, Issue 6 , 2004 , Pages 1621-1625 ; 00029939 (ISSN) Akbari, S ; Aryapoor, M ; Sharif University of Technology
    Let F be an algebraically closed field and T: Mn(F) → Mn(F) be a linear transformation. In this paper we show that if T preserves at least one eigenvalue of each matrix, then T preserves all eigenvalues of each matrix. Moreover, for any infinite field F (not necessarily algebraically closed) we prove that if T: Mn(F) → M n(F) is a linear transformation and for any A ∈ Mn(F) with at least an eigenvalue in F, A and T(A) have at least one common eigenvalue in F, then T preserves the characteristic polynomial  

    On Triangularizability of a Group of Operators

    , Article Results in Mathematics ; Volume 61, Issue 1-2 , 2012 , Pages 57-61 ; 14226383 (ISSN) Fanaï, H. R ; Mahshid, M. K ; Sharif University of Technology
    Let G be a group of invertible linear transformations on a finite-dimensional vector space over an algebraically closed field. We show that if G = H V K, where H is a normal subgroup consisting of singleton spectrum operators and K is a triangularizable subgroup, then G is triangularizable  

    Tunable delay line based on Fourier-transformation and linear phase modulation with high time-bandwidth product

    , Article Photonische Netze - 13. ITG-Fachtagung 2020 ; 2020 , Pages 229-231 Mokhtari, A ; Preubler, S ; Jamshidi, K ; Akbari, M ; Schneider, T ; Sharif University of Technology
    VDE Verlag GmbH  2020
    We recruit basic properties of Fourier transformation to realize an electrically tunable delay line and increase the delay by creating a loop in the structure. The proposed method has been experimentally tested and verified for up to 5 roundtrips. The relative delay/advancement was increased up to 5 times compared to the original setup while preserving the original setup's advantages. © VDE VERLAG GMBH  

    Conditions on decomposing linear systems with more than one matrix to block triangular or diagonal form

    , Article IEEE Transactions on Automatic Control ; Volume 60, Issue 1 , May , 2015 , Pages 233-239 ; 00189286 (ISSN) Mesbahi, A ; Haeri, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    This technical note provides necessary and sufficient conditions to determine that a linear system with more than one matrix in its state-space representation can be decomposed into cascade or separate sub-systems. In order to perform such decomposition, one needs to determine a linear transformation matrix. Furthermore, the given conditions are adapted to a simple but effective condition to derive all possible scalar sub-systems for a given linear system. Numerical examples are provided to demonstrate the applicability of the presented results  

    Structural synthesis of 5 DoFs 3T2R parallel manipulators with prismatic actuators on the base

    , Article Robotics and Autonomous Systems ; Volume 58, Issue 3 , 2010 , Pages 307-321 ; 09218890 (ISSN) Motevalli, B ; Zohoor, H ; Sohrabpour, S ; Sharif University of Technology
    A method is presented to synthesize 5 degrees of freedom (DoFs) of 3 translational and 2 rotational (3T2R) parallel kinematic structures. This method is based on the theory of linear transformation and geometrical analysis. Central to this method is a set of novel 5 DoFs 3T2R parallel mechanisms (PMs). Based on the legs configuration, the generated mechanisms are classified. Moreover, the promising mechanisms of each class are introduced with respect to some criteria, i.e.: (a) degree of coupling between the actuators and degrees of freedom; (b) easy kinematics and control command; (c) easy construction (or low cost construction); and, (d) manufacturability. With reference to these criteria,... 

    Tracking the 3D configuration of human joint using an MR image registration technique

    , Article ASME 2010 5th Frontiers in Biomedical Devices Conference and Exhibition, BIOMED 2010, 20 September 2010 through 21 September 2010 ; 2010 , Pages 93-94 ; 9780791849453 (ISBN) Mostafavi Yazdi, S. K ; Farahmand, F ; Jafari, A ; Sharif University of Technology
    Surface registration is a necessary step and widely used in medical image-aided surgery. It's relevance to medical imaging is that there is much useful anatomical information in the form of collected surface points which originate from complimentary modalities. In this study, the kinematic relations between two point clouds with different coordinate definitions have been generated. Using Influence Method of surface modeling for extracting point clouds functions, the transformation matrix would be resulted. The proposed method was applied for an experimental femur data points(651 points) using the MRI images. These data points were transformed in a 30 degrees flexion of knee. This... 

    Non-linear metric learning using pairwise similarity and dissimilarity constraints and the geometrical structure of data

    , Article Pattern Recognition ; Volume 43, Issue 8 , August , 2010 , Pages 2982-2992 ; 00313203 (ISSN) Soleymani Baghshah, M ; Bagheri Shouraki, S ; Sharif University of Technology
    The problem of clustering with side information has received much recent attention and metric learning has been considered as a powerful approach to this problem. Until now, various metric learning methods have been proposed for semi-supervised clustering. Although some of the existing methods can use both positive (must-link) and negative (cannot-link) constraints, they are usually limited to learning a linear transformation (i.e., finding a global Mahalanobis metric). In this paper, we propose a framework for learning linear and non-linear transformations efficiently. We use both positive and negative constraints and also the intrinsic topological structure of data. We formulate our metric... 

    Fast homography refinement in soccer videos

    , Article 9th Iranian Conference on Machine Vision and Image Processing, 18 November 2015 through 19 November 2015 ; Volume 2016-February , 2015 , Pages 185-188 ; 21666776 (ISSN) ; 9781467385398 (ISBN) Hadian, M ; Kasaei, S ; Sharif University of Technology
    IEEE Computer Society 
    Sports video analysis and camera calibration are important applications which rely on accurate homography computation as a challenging task. Homography refinement is an important step in the task of accurate homography computation and homography tracking. Also, in certain applications (such as homography tracking) the process speed is of great importance. A robust and fast method for accurate refinement of highly inaccurate homographies in soccer video frames is proposed in this paper. To achieve that goal, a new homography model fitting method named the point-line (PL) method is proposed. It uses point-line correspondences to compute the homography, rather than point correspondences or line... 

    Transformation of sliding motion to rolling during spheres collision

    , Article Granular Matter ; Volume 19, Issue 4 , 2017 ; 14345021 (ISSN) Nejat Pishkenari, H ; Kaviani Rad, H ; Jafari Shad, H ; Sharif University of Technology
    In this research, we have investigated the three-dimensional elastic collision of two balls, based on friction in the tangential plane. Our aim is to offer analytical closed form relations for post collision parameters such as linear and angular velocities, collision time and tangential and normal impulse in three dimensions. To simplify the problem, stick regime is not considered. In other words, balls have a low tangential coefficient of restitution. Sliding, sliding then rolling, and rolling at the beginning of contact are three cases that can occur during impact which have been considered in our research. The normal interaction force is described by the Hertz contact force and... 

    A non parametric approach to monitor simple linear profiles in phases I and II

    , Article Communications in Statistics - Theory and Methods ; Volume 46, Issue 11 , 2017 , Pages 5203-5222 ; 03610926 (ISSN) Sayyad, A ; Akhavan Niaki, S. T ; Afshar Najafi, B ; Sharif University of Technology
    Taylor and Francis Inc  2017
    In this paper, a non parametric approach is first proposed to monitor simple linear profiles with non normal error terms in Phase I and Phase II. In this approach, two control charts based on a transformation technique and decision on beliefs are designed in order to monitor the intercept and the slope, simultaneously. Then, some simulation experiments are performed in order to evaluate the performance of the proposed control charts in Phase II under both step and drift shifts in terms of out-of-control average run length (ARL1). Besides, the performance of the proposed control charts is compared to the ones of seven other existing schemes in the literature. Simulation results show that the... 

    Sampling and recovery of binary shapes via low-rank structures

    , Article 13th International Conference on Sampling Theory and Applications, SampTA 2019, 8 July 2019 through 12 July 2019 ; 2019 ; 9781728137414 (ISBN) Razavikia, S ; Zamani, H ; Amini, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    The binary-valued images usually represent shapes. Therefore, the recovery of binary images from samples is often linked with recovery of shapes, where certain parametric structures are assumed on the shape. In this paper, we study the recovery of shape images with the perspective of low-rank matrix recovery. The matrix of such images is not automatically low-rank. Therefore, we consider the Hankel transformation of binary images in order to apply tools in low-rank matrix recovery. We introduce an ADMM technique for the reconstruction which is numerically confirmed to yield suitable results. We also analyze the sampling requirement of this process based on the theory of random matrices. ©... 

    Learning a metric when clustering data points in the presence of constraints

    , Article Advances in Data Analysis and Classification ; Volume 14, Issue 1 , 2020 , Pages 29-56 Abin, A. A ; Bashiri, M. A ; Beigy, H ; Sharif University of Technology
    Springer  2020
    Learning an appropriate distance measure under supervision of side information has become a topic of significant interest within machine learning community. In this paper, we address the problem of metric learning for constrained clustering by considering three important issues: (1) considering importance degree for constraints, (2) preserving the topological structure of data, and (3) preserving some natural distribution properties in the data. This work provides a unified way to handle different issues in constrained clustering by learning an appropriate distance measure. It has modeled the first issue by injecting the importance degree of constraints directly into an objective function.... 

    Implementation of optical tracker system for marker-based human motion tracking

    , Article 15th IASTED International Conference on Applied Simulation and Modelling, Rhodes, 26 June 2006 through 28 June 2006 ; Volume 2006 , 2006 , Pages 252-257 ; 0889865612 (ISBN); 9780889865617 (ISBN) Colahi, A ; Hoviatalab, M ; Rezaeian, T ; Alizadeh, M ; Bostan, M ; Sharif University of Technology
    In this paper a complete design of a high speed optical human motion tracking system has been described for biomechanical human motion analysis and animation craft applications. The main core of the image processing unit that is implemented by the differential algorithm procedure and some intelligent and conservative procedures that facilitate the search algorithm have also been proposed and implemented for the processing of human motions tracking images. In the next step an optimized modified direct linear transformation (MDLT) method has been used to reconstruct 3D locations of markers as an input data for animation unit. The low computational cost and the high precision in detecting and... 

    Optimal VM-to-user mapping in cloud environment based on sustainable strategy space theory

    , Article Cluster Computing ; Volume 24, Issue 4 , 2021 , Pages 3229-3247 ; 13867857 (ISSN) Khanzadi, P ; Adabi, S ; Majidi, B ; Movaghar, A ; Sharif University of Technology
    Springer  2021
    According to the previous studies in the field of economics-oriented cloud resource allocation using game theory, finding an equilibrium point for price is difficult in many cases. This is due to the stochastic situations of the cloud market. So, to tackle this problem we should find a space to describe behavior of the players’ strategies that be independent from the equilibrium point. Therefore, a new algorithm for VM-to-user mapping in the cloud market called VMUMA is proposed. For designing VMUMA, the cloud market is modeled by game theory. VMUMA is based on Sustainable Strategy Space Theory (SSST) in which, each stability and instability of the player’s strategies in the game are defined... 

    Semi-supervised metric learning using pairwise constraints

    , Article 21st International Joint Conference on Artificial Intelligence, IJCAI-09, Pasadena, CA, 11 July 2009 through 17 July 2009 ; 2009 , Pages 1217-1222 ; 10450823 (ISSN) ; 9781577354260 (ISBN) Soleymani Baghshah, M ; Bagheri Shouraki, S ; Sharif University of Technology
    Distance metric has an important role in many machine learning algorithms. Recently, metric learning for semi-supervised algorithms has received much attention. For semi-supervised clustering, usually a set of pairwise similarity and dissimilarity constraints is provided as supervisory information. Until now, various metric learning methods utilizing pairwise constraints have been proposed. The existing methods that can consider both positive (must-link) and negative (cannot-link) constraints find linear transformations or equivalently global Mahalanobis metrics. Additionally, they find metrics only according to the data points appearing in constraints (without considering other data... 

    Efficient algebraic solution for elliptic target localisation and antenna position refinement in multiple-input-multiple-output radars

    , Article IET Radar, Sonar and Navigation ; Volume 13, Issue 11 , 2019 , Pages 2046-2054 ; 17518784 (ISSN) Amiri, R ; Behnia, F ; Noroozi, A ; Sharif University of Technology
    Institution of Engineering and Technology  2019
    In this study, an algebraic closed-form method for jointly locating the target and refining the antenna positions in multiple-input-multiple-output radar systems is proposed. First, a set of linear equations is formed by non-linear transformation and nuisance parameters elimination, and then, an estimate of the target position is obtained by employing a weighted least-squares estimator. To jointly refine the target and antenna positions, the associated error terms are estimated in the sequence. The proposed method is shown analytically and confirmed by simulations to attain the Cramér-Rao lower bound performance under small-error conditions. Numerical simulations are given to support the... 

    Design a Cartesian, Decoupled and Isotropic 5-DoF Parallel Manipulator

    , M.Sc. Thesis Sharif University of Technology Davoudi Dehkordi, Matin (Author) ; Zohoor, Hassan (Supervisor)
    Given the optimum design importance of parallel mechanisms, characteristics such as degree of freedom, decoupled and isotropic in structural synthesis of these mechanisms are considered. Also, due to less attention to the development of 5-DoF parallel manipulators, in this research, the improvement of this types of mechanisms is considered. In this research effort to design 5-DoF cartesian, decoupled and isotropic parallel manipulators leads to represent four numbers of this type of mechanisms with 3T2R and 2T3R degrees of freedom. Represented PMs verified with linear transformation theory. Morever by using Jacobian, they more analyzed for their decoupled and isotropic specifications in... 

    Statistical monitoring of autocorrelated simple linear profiles based on principal components analysis

    , Article Communications in Statistics - Theory and Methods ; Volume 44, Issue 21 , Nov , 2015 , Pages 4454-4475 ; 03610926 (ISSN) Akhavan Niaki, S. T ; Khedmati, M ; Soleymanian, M. E ; Sharif University of Technology
    Taylor and Francis Inc  2015
    In this article, a transformation method using the principal component analysis approach is first applied to remove the existing autocorrelation within each profile in Phase I monitoring of autocorrelated simple linear profiles. This easy-to-use approach is independent of the autocorrelation coefficient. Moreover, since it is a model-free method, it can be used for Phase I monitoring procedures. Then, five control schemes are proposed to monitor the parameters of the profile with uncorrelated error terms. The performances of the proposed control charts are evaluated and are compared through simulation experiments based on different values of autocorrelation coefficient as well as different... 

    Nonlinear transient transfinite element thermal analysis of thick-walled FGM cylinders with temperature-dependent material properties

    , Article Meccanica ; Volume 45, Issue 3 , June , 2010 , Pages 305-318 ; 00256455 (ISSN) Azadi, M ; Shariyat, M ; Sharif University of Technology
    An algorithm for investigation of nonlinear systems by the transfinite element method is presented. Basically, the transformation techniques have been developed for linear systems. Nonlinear transient heat transfer of a thick FGM cylinder with temperature-dependent material properties is investigated in the present paper to clarify the proposed algorithm. Two main novelties of the present research are: (1) incorporating the temperature-dependency of the material properties in the thermal analysis which lead to highly non-linear governing equations and (2) proposing an updating numerical transfinite element procedure to solve the resulted highly nonlinear governing equations. To reduce the... 

    Nonlinear blind source separation for sparse sources

    , Article European Signal Processing Conference, 28 August 2016 through 2 September 2016 ; Volume 2016-November , 2016 , Pages 1583-1587 ; 22195491 (ISSN) ; 9780992862657 (ISBN) Ehsandoust, B ; Rivet, B ; Jutten, C ; Babaie Zadeh, M ; Sharif University of Technology
    European Signal Processing Conference, EUSIPCO  2016
    Blind Source Separation (BSS) is the problem of separating signals which are mixed through an unknown function from a number of observations, without any information about the mixing model. Although it has been mathematically proven that the separation can be done when the mixture is linear, there is not any proof for the separability of nonlinearly mixed signals. Our contribution in this paper is performing nonlinear BSS for sparse sources. It is shown in this case, sources are separable even if the problem is under-determined (the number of observations is less than the number of source signals). However in the most general case (when the nonlinear mixing model can be of any kind and there...