Papers by hamid mesgarani
Circuits, Systems, and Signal Processing
In this paper, the improved wavelet transform domain least mean squares (IWTDLMS) adaptive algori... more In this paper, the improved wavelet transform domain least mean squares (IWTDLMS) adaptive algorithm is established. The IWTDLMS algorithm has a faster convergence speed than the conventional WTDLMS for colored input signals. Since the performances of WTDLMS and IWTDLMS are degraded in impulsive noise interference, the IWTDLMS sign algorithm (IWTDLMS-SA) is proposed. In comparison with IWTDLMS, the IWTDLMS-SA has lower computational complexity. In order to improve the performance of IWTDLMS-SA, the variable step-size IWTDLMS-SA (VSS-IWTDLMS-SA) is introduced. The VSS-IWTDLMS-SA is derived by minimizing the 1-norm of the a posteriori error vector. To increase the tracking ability of the VSS-IWTDLMS-SA, the modified VSS-IWTDLMS-SA (MVSS-IWTDLMS-SA)is presented. The simulation results demonstrate that the proposed algorithms have a faster convergence rate and lower misadjustment than the conventional WTDLMS. The robustness feature of the IWTDLMS-SA, VSS-IWTDLMS-SA, and MVSS-IWTDLMS-SA against impulsive noises is also verified through several experiments in a system identification setup.
This paper applies numerical approximations of combination of Laplacian and biharmonic operator f... more This paper applies numerical approximations of combination of Laplacian and biharmonic operator for edge detection. The Laplacian of an image combine the second order derivatives to detect edge of an image. Numerical approximation are computed by finite difference schemes of 4 h O then we apply Richardson’s extrapolation technique in order to achieve better approximation of 6 h O for edge detection and PSNR values are presented to show improvement in results of edge detection for Richardson extrapolation. Finally the experimental results of extrapolation edge detector for comparison with Laplacian and Canny edge detectors are presented.
Mathematical Sciences, 2022
Abstract: In this paper, Semi-orthogonal (SO) B-spline scaling functions and wavelets and their d... more Abstract: In this paper, Semi-orthogonal (SO) B-spline scaling functions and wavelets and their dual functions are presented to approximate the solutions of linear and non-linear second order Fredholm integro-differential equations. The B-spline scaling functions and wavelets, their properties and the operational matrices of derivative for this functions are presented to reduce the solution of linear and nonlinear Fredholm integro-differential equations to the solution of algebraic equations. Key words: Semi-orthogonal • B-spline wavelet • Non-linear integro-differential equation
Journal of Zankoy Sulaimani - Part A, 2020
Scientific Journal of Pure and Applied Sciences, 2013
Shooting method has been applied to investigating different parameters of a 2D viscous flow which... more Shooting method has been applied to investigating different parameters of a 2D viscous flow which is electrically conducting over a non-linear as well as a semi-infinite stretching sheet. In this study, the influences of a chemical reaction and magnetic field have also been considered and analyzed. The governing differential equations, concentration field and heat transfer, are firstly reduced to a set of coupled non-linearly ordinary differential equations (ODEs) and then have been processed and solved numerically by the shooting method. The numerical results of the concentration field and heat transfer are shown through graphs.
In this paper for a given set of real or complex interval numbers $sigma$ satisfying special co... more In this paper for a given set of real or complex interval numbers $sigma$ satisfying special conditions, we find an interval nonnegative matrix $C$ such that for each point set $delta$ of given interval spectrum $sigma$, there exists a point matrix $A$ of $C$ such that $delta$ is its spectrum. We also study some conditions for the solution existence of the problem.
شور‌هلاقم‌نیا‌رد ی کجوم‌و‌سایقم‌عباوت‌رب‌ینتبم‌یددع یب‌یاه اب‌هنیهب‌لرتنک‌لئاسم‌لح‌یارب‌یب... more شور‌هلاقم‌نیا‌رد ی کجوم‌و‌سایقم‌عباوت‌رب‌ینتبم‌یددع یب‌یاه اب‌هنیهب‌لرتنک‌لئاسم‌لح‌یارب‌یبعکم‌نیلاپسا لارگتنا هلداعم ای یلارگتنا هلداعم یکیمانید متسیس ثحب لیسنارفید یم دوش . رتام سی یتایلمع یاه و قتشم لارگتنا لصاح برض ود رب کجوم‌راد یب‌یاه یبعکم‌نیلاپسا مه‌شور، لارگتنا‌هدعاق‌و‌یلحم سواگ‌یریگ هتسسگ‌یارب‌ردناژل یزاس لئسم ۀ لئسم‌کی‌هب‌نآ‌لیدبت‌و‌هتسویپ‌هنیهب‌لرتنک ۀ همانرب ریغ‌یزیر هب‌یطخ یم‌هتفرگ‌راک دوش . و‌لرتنک‌عباوت‌ییارگمه مه‌و‌یداهنشیپ‌شور‌زا‌لصاح‌یبیرقت‌هنیهب‌رایعم‌کعبات‌و‌تلاح آ‌یاطخ‌یلااب‌نارک‌نینچ هن ا ب ه یم‌هدروآ‌تسد دنوش . لاثم یاه یددع دیا‌ندوب‌دیفم‌و‌تقد،ییاراک ۀ یم‌ناشن‌ار‌یداهنشیپ دنهد .
International Journal of Numerical Methods for Heat & Fluid Flow, 2021
Purpose The purpose of this study is to use the method of lines to solve the two-dimensional nonl... more Purpose The purpose of this study is to use the method of lines to solve the two-dimensional nonlinear advection–diffusion–reaction equation with variable coefficients. Design/methodology/approach The strictly positive definite radial basis functions collocation method together with the decomposition of the interpolation matrix is used to turn the problem into a system of nonlinear first-order differential equations. Then a numerical solution of this system is computed by changing in the classical fourth-order Runge–Kutta method as well. Findings Several test problems are provided to confirm the validity and efficiently of the proposed method. Originality/value For the first time, some famous examples are solved by using the proposed high-order technique.
Alexandria Engineering Journal, 2022
In this paper, the space-time fractional advection-diffusion equation (STFADE) is considered in t... more In this paper, the space-time fractional advection-diffusion equation (STFADE) is considered in the finite domain that the time and space derivatives are the Caputo fractional derivative. At first, a quadratic interpolation with convergence order O s 3Àa ð Þ is applied to obtain the semidiscrete in time variable. Then, the Chebyshev collocation method of the fourth kind has been used to approximate the spatial fractional derivative. In addition, the energy method has been employed to show the unconditional stability and gained convergence order of the time-discrete scheme. Finally, the accuracy of the numerical method is analyzed and showed that our method is much more accurate than existing techniques.
Numerical Methods for Partial Differential Equations, 2020
Fractional diffusion equations include a consistent and efficient explanation of transport phenom... more Fractional diffusion equations include a consistent and efficient explanation of transport phenomena that manifest abnormal diffusion, that cannot be often represented by second‐order diffusion equations. In this article, a two‐dimensional space fractional diffusion equation (SFDE‐2D) with nonhomogeneous and homogeneous boundary conditions is considered in Caputo derivative sense. An instant and nevertheless accurate scheme is obtained by the finite‐difference discretization to get the semidiscrete in temporal derivative with convergence order O(δτ2) . Moreover, space fractional derivative can be approximated based on the Chebyshev polynomials of second kind which are powerful methods for basing the operational matrix. The convergence and stability of the proposed scheme are discussed theoretically in detail. Finally, two numerical problems with an exact solution are given that numerical results show the effectiveness of the new techniques. These schemes can be simply extended to three spatial dimensions, which will be the subject of our subsequent research.
International Journal of Applied and Computational Mathematics, 2020
The present paper is primarily aimed at obtaining the numerical solution of space fractional adve... more The present paper is primarily aimed at obtaining the numerical solution of space fractional advection-diffusion equation including two fractional space derivatives of order. At the first stage, a difference approach with the second-order accuracy is formulated to obtain a semidiscrete scheme. Unconditional stability and convergence analysis has been analyzed. At the second stage, the spatial discretization is accomplished by means of the second kind shifted Chebyshev polynomials. Two examples are investigated, and numerical results are reported to confirm the theoretical results.
Mathematical Sciences, 2019
We consider Fredholm integral equation of the first kind with noisy data and use Landweber-type i... more We consider Fredholm integral equation of the first kind with noisy data and use Landweber-type iterative methods as an iterative solver. We compare regularization property of Tikhonov, truncated singular value decomposition and the iterative methods. Furthermore, we present a necessary and sufficient condition for the convergence analysis of the iterative method. The performance of the iterative method is shown and compared with modulus-based iterative methods for the constrained Tikhonov regularization.
Circuits, Systems, and Signal Processing, 2019
The present study introduces a robust variable step-size affine projection sign adaptive algorith... more The present study introduces a robust variable step-size affine projection sign adaptive algorithm (RVSS-APSA) in impulsive noise environments. In the proposed RVSS-APA, the weight coefficients are updated based on the minimization of 2-norm of the a posteriori error and the step size changes according to the minimization of 1norm of the a posteriori error. This algorithm reduces the steady-state misalignment and increases the convergence rate for colored input signal as well as with or without impulsive noise interference. Also, a new simple reset algorithm is proposed to improve the tracking ability of the introduced algorithm. The simulation results demonstrate a good performance for the proposed algorithm in different situations.
Digital Signal Processing, 2017
In this paper, the WTDLMS adaptive algorithm is established based on the multiple-constraint opti... more In this paper, the WTDLMS adaptive algorithm is established based on the multiple-constraint optimization criterion. Furthermore, the WTDLMS with dynamic subband-coefficients update (WTDLMS-DU) is introduced. In this algorithm, the coefficients belonging to a certain subbands are dynamically selected for the update. The optimum selection of the subband-coefficients is derived by the largest decrease of the mean-square deviation. The WTDLMS-DU has a fast convergence speed and a low steady-state error similar to the WTDLMS. In addition, the proposed algorithm has lower computational complexity in comparison to WTDLMS algorithm. The good performance of WTDLMS-DU is demonstrated in various applications such as system identification, linear prediction, and acoustic echo cancellation. Also, a general formalism for the establishment and the theoretical mean-square performance analysis of the family of WTDLMS adaptive algorithms such as WTDLMS, WTDLMS with partial update (WTDLMS-PU), and the proposed WTDLMS-DU are presented. The transient, the steady-state, and the stability bounds of these algorithms are studied in a unified way. This analysis is based on energy conservation arguments and does not need to assume a Gaussian or white distribution for the regressors. It is demonstrated through simulations that the results are useful in predicting the performance of the family of WTDLMS adaptive filter algorithms.
Scientia Iranica, 2018
In this paper, the wavelet transform domain least mean squares (WTDLMS) adaptive algorithm with v... more In this paper, the wavelet transform domain least mean squares (WTDLMS) adaptive algorithm with variable step-size (VSS) is established. The step-size changes according to the largest decrease in mean square deviation. To keep the computational complexity low, the Haar wavelet transform (HWT) is utilized as a transform. In addition, the mean square performance analysis of the VSS-WTDLMS is studied in the stationary and nonstationary environments and the theoretical relations for transient and steady-state performances are established. The simulation results show that the proposed VSS-WTDLMS has faster convergence rate and lower misadjustment than conventional WTDLMS. The theoretical relations are also verified by presenting various experimental results.
The PageRank (PR) algorithm is the base of Google search engine. In this paper, we study the Page... more The PageRank (PR) algorithm is the base of Google search engine. In this paper, we study the PageRank sequence for undirected graphs of order six by PR vector. Then, we provide an ordering for graphs by variance of PR vector which it’s variation is proportional with variance of degree sequence. Finally, we introduce a relation between domination number and PR-variance of graphs.
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Papers by hamid mesgarani