In tomography from a small number of projections it is necessary to apply the algorithms that allow to use prior information about the solution. The Gerchberg-Papoulis algorithm (G-P), based on the central slice theor...
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ISBN:
(纸本)9781424421336
In tomography from a small number of projections it is necessary to apply the algorithms that allow to use prior information about the solution. The Gerchberg-Papoulis algorithm (G-P), based on the central slice theorem in Fourier space, is known as one of the most effective iterative methods for few-projection tomography in parallel scanning geometries. This algorithm has not been studied for fan-beam geometries, because a central slice theorem is lacking. In this paper, we state a recently developed central slice theorem for fan-beam geometries, and on this basis we develop a new iterative G-P algorithm. In numerical simulation two versions are *** study how additive random noise in the projections influences the accuracy of the reconstructions, and we give regularization criteria for suppressing random noise in the measurements.
Improved clonal selection algorithms were proposed as a method to implement optimal iterative learning control algorithms. The strength of the method is that it not only can cope with non-minimum phase plants and nonl...
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Improved clonal selection algorithms were proposed as a method to implement optimal iterative learning control algorithms. The strength of the method is that it not only can cope with non-minimum phase plants and nonlinear plants even there are uncertainties in their models, but also can deal with constraints on input signals conveniently by a specially designed mutation operator. Simulations show that the convergence speed is satisfactory regardless of the nature of the plants and whether or not the models of the plants are precise.
Low rank approximations of matrices have been widely used in pattern recognition and machine learning. Based on a sequence of matrices, a generalized low rank approximation problem was presented and an iterative schem...
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Low rank approximations of matrices have been widely used in pattern recognition and machine learning. Based on a sequence of matrices, a generalized low rank approximation problem was presented and an iterative scheme was given by Liang and Shi recently proposed an analytical scheme for this approximation problem. In this paper, we identify the weakness in their scheme and prove that their algorithm is incorrect. (C) 2007 Elsevier Ltd. All rights reserved.
In this paper, an iterative high-resolution DOA algorithm is proposed for DOA estimation for CDMA systems. The algorithmiteratively removes detected signals from the received data and searches the residue spatial spe...
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ISBN:
(纸本)9781424421077
In this paper, an iterative high-resolution DOA algorithm is proposed for DOA estimation for CDMA systems. The algorithmiteratively removes detected signals from the received data and searches the residue spatial spectrum for further signals. It does not require any computationally expensive eigen decomposition or spatial smoothing in coherent multipath scenarios. Results are presented illustrating high-resolution at significantly lower SNR levels than those obtained by classical DOA algorithms such as MUSIC and MVM.
A new set of higher order hierarchical basis functions is proposed for expansion of the current in electrical field integral equations (EFIE) solved by multilevel fast multipole algorithm (MLFMA) for the cavity scatte...
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ISBN:
(纸本)9781424418794
A new set of higher order hierarchical basis functions is proposed for expansion of the current in electrical field integral equations (EFIE) solved by multilevel fast multipole algorithm (MLFMA) for the cavity scattering problem. The hierarchical two-level spectral preconditioning technique is developed to solve EFIE with multiple right-hand sides arising in monostatic radar cross section (RCS) calculations. The sparse approximate inverse (SAI) preconditioner based on the higher order hierarchical basis functions is used to damp the high frequencies of the error and the low frequencies is eliminated by a spectral preconditioner in a two-level manner defined on the lower order basis functions. The spectral preconditioner is combined with SAI preconditioner to obtain a hierarchical two-level spectral preconditioner. This newly constructed hierarchical two-level spectral preconditioner is used to speed up the restarted GMRES iterative algorithm. Numerical experiments indicate that the new preconditioner is efficient for the MLFMA and can significantly reduce both the iteration number and computational time.
Vision plays the most important role in human perception, which is limited to only the visual band of the electromagnetic spectrum. Therefore, the need for Radar imaging systems, to recover some sources that are not w...
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ISBN:
(纸本)9781424417513
Vision plays the most important role in human perception, which is limited to only the visual band of the electromagnetic spectrum. Therefore, the need for Radar imaging systems, to recover some sources that are not within human visual band, is raised. This paper presents a new algorithm for Synthetic Aperture Radar (SAR) images segmentation based on thresholding technique. Generally, segmentation of a SAR image falls into two categories;one based on grey levels and the other based on texture. The present paper deals with SAR images segmentation based on grey levels. We developed a new formula using Minimum Cross Entropy Thresholding (MCET) method for estimating optimal threshold value based on Gamma distribution to analyzing data on images;that means histogram of SAR images is assumed to be a mixture of Gamma distributions. The proposed method is iterative which decreases the number of operation to converge tends to the optimal solution. It is applied on bi-modal and multimodal scenarios. The results obtained are promising.
The scattering of light within paper and the ink penetration in the substrate are the key factors which affect the color reproduction. A reflectance model for color halftone prints is introduced in this paper which co...
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ISBN:
(纸本)9780819469793
The scattering of light within paper and the ink penetration in the substrate are the key factors which affect the color reproduction. A reflectance model for color halftone prints is introduced in this paper which considers these factors. The model is obtained by the extended Murray-Davies model and iterative algorithm. The model described in this paper contains two parameters, n and v. The n factor equals to the sum of w and v. The w factor relates to the optical spread function of paper relative to the spatial frequency of the halftone dots. The v factor relates to the distribution of colorant within the dots. The value of n and v are obtained by simulation according to the experimental data. For offset lithographic halftone data at 1501pi, the value of n and V are 1.578 and 0.02, thermal wax transfer halftone (n=2.292, v=0.0209) and stochastic halftone (n=1.1853, v=-0.006).
In this paper, we propose two iterative algorithms to solve the matrix equation AXB + (CXD)-D-T = E. The first algorithm is applied when the matrix equation is consistent. In this case, for any (special) initial matri...
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In this paper, we propose two iterative algorithms to solve the matrix equation AXB + (CXD)-D-T = E. The first algorithm is applied when the matrix equation is consistent. In this case, for any (special) initial matrix X-1, a solution (the minimal Frobenius norm solution) can be obtained within finite iteration steps in the absence of roundoff errors. The second algorithm is applied when the matrix equation is inconsistent. In this case, for any (special) initial matrix X-1, a least squares solution (the minimal Frobenius norm least squares solution) can be obtained within finite iteration steps in the absence of roundoff errors. Some examples verify the efficiency of these algorithms. (c) 2006 Elsevier Inc. All rights reserved.
In this paper we introduce and study a new system of nonlinear variational inclusions with (A, eta)-accretive mappings in Banach spaces. By using the resolvent operator associated with (A, eta)-accretive mappings, we ...
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In this paper we introduce and study a new system of nonlinear variational inclusions with (A, eta)-accretive mappings in Banach spaces. By using the resolvent operator associated with (A, eta)-accretive mappings, we construct some new iterative algorithms for approximating the solution of this system of variational inclusions. We also prove the existence of solutions and the convergence of the sequences generated by the algorithm in Banach spaces. The results presented in this paper extend and improve some known results in the literature. (c) 2007 Elsevier Ltd. All rights reserved.
In this paper, we study the iterative algorithm and convergence theorems for F-implicit generalized variational inequalities problem (F-IGVIP). By employing our earlier works ([6], Theorem 2.2), we establish several i...
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In this paper, we study the iterative algorithm and convergence theorems for F-implicit generalized variational inequalities problem (F-IGVIP). By employing our earlier works ([6], Theorem 2.2), we establish several iterative convergence results for F-IGVIP. The algorithm and convergence results are new for solving the strong solution of F-IGVIP. Furthermore, new algorithms and convergence theorems for F-implicit generalized complementarity problem (F-IGCP) are also discussed.
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