Compressed sensing (CS) theory has been recently applied in Magnetic Resonance Imaging (MRI) to accelerate the overall imaging process. In the CS implementation, various algorithms have been used to solve the nonlinea...
详细信息
ISBN:
(纸本)9781424441242
Compressed sensing (CS) theory has been recently applied in Magnetic Resonance Imaging (MRI) to accelerate the overall imaging process. In the CS implementation, various algorithms have been used to solve the nonlinear equation system for better image quality and reconstruction speed. However, there are no explicit criteria for an optimal CS algorithm selection in the practical MRI application. A systematic and comparative study of those commonly used algorithms is therefore essential for the implementation of CS in MRI. In this work, three typical algorithms, namely, the Gradient Projection For Sparse Reconstruction (GPSR) algorithm, interior-point algorithm (l(1)_ls), and the Stagewise Orthogonal Matching Pursuit (StOMP) algorithm are compared and investigated in three different imaging scenarios, brain, angiogram and phantom imaging. The algorithms' performances are characterized in terms of image quality and reconstruction speed. The theoretical results show that the performance of the CS algorithms is case sensitive;overall, the StOMP algorithm offers the best solution in imaging quality, while the GPSR algorithm is the most efficient one among the three methods. In the next step, the algorithm performances and characteristics will be experimentally explored. It is hoped that this research will further support the applications of CS in MRI.
An interior-point trust-region algorithm is proposed for minimization of a convex quadratic objective function over a general convex set. The algorithm uses a trust-region model to ensure descent on a suitable merit f...
详细信息
An interior-point trust-region algorithm is proposed for minimization of a convex quadratic objective function over a general convex set. The algorithm uses a trust-region model to ensure descent on a suitable merit function. The complexity of our algorithm is proved to be as good as the interior-point polynomial algorithm.
Based on the idea of Dikin-type primal-dual affine scaling method for linear program-ming,we describe a high-order Dikin-type algorithm for P_*(κ)-matrix linear complementarity problem in a wide neighborhood of the c...
详细信息
Based on the idea of Dikin-type primal-dual affine scaling method for linear program-ming,we describe a high-order Dikin-type algorithm for P_*(κ)-matrix linear complementarity problem in a wide neighborhood of the central path,and its polynomial-time complexity bound is ***,two numerical experiments are provided to show the effectiveness of the proposed algorithms.
This note points out an error in the local quadratic convergence proof of the predictor-corrector interior-point algorithm for solving the semidefinite linear complementarity problem based on the Alizadeh-Haeberly-Ove...
详细信息
This note points out an error in the local quadratic convergence proof of the predictor-corrector interior-point algorithm for solving the semidefinite linear complementarity problem based on the Alizadeh-Haeberly-Overton search direction presented in [M. Kojima, M. Shida, and S. Shindoh, SIAM J. Optim., 9 (1999), pp. 444-465]. Their algorithm is slightly modified and the local quadratic convergence of the resulting method is established.
Based on the idea of Dikin-type primal-dual affine scaling method for linear program-ming,we describe a high-order Dikin-type algorithm for P(κ)-matrix linear complementarity problem in a wide neighborhood of the c...
详细信息
Based on the idea of Dikin-type primal-dual affine scaling method for linear program-ming,we describe a high-order Dikin-type algorithm for P(κ)-matrix linear complementarity problem in a wide neighborhood of the central path,and its polynomial-time complexity bound is ***,two numerical experiments are provided to show the effectiveness of the proposed algorithms.
We consider the problem of finding an c-optimal solution of a standard linear program with real data, i.e., of finding a feasible point at which the objective function value differs by at most epsilon from the optimal...
详细信息
We consider the problem of finding an c-optimal solution of a standard linear program with real data, i.e., of finding a feasible point at which the objective function value differs by at most epsilon from the optimal value. In the worst-case scenario the best complexity result to date guarantees that such a point is obtained in at most O(root n vertical bar ln epsilon vertical bar) steps of an interior-point method. We show that the expected value of the number of steps required to obtain an epsilon-optimal solution for a probabilistic linear programming model is at most O(min {n(1.5), m root n ln(n)}) + log(2)(vertical bar ln epsilon vertical bar). (C) 2007 Elsevier Inc. All rights reserved.
Two corrector - predictor interiorpointalgorithms are proposed for solving monotone linear complementarity problems. The algorithms produce a sequence of iterates in the N-infinity(-) neighborhood of the central pat...
详细信息
Two corrector - predictor interiorpointalgorithms are proposed for solving monotone linear complementarity problems. The algorithms produce a sequence of iterates in the N-infinity(-) neighborhood of the central path. The first algorithm uses line search schemes requiring the solution of higher order polynomial equations in one variable, while the line search procedures of the second algorithm can be implemented in O(m n(1+alpha)) arithmetic operations, where n is the dimension of the problems, alpha is an element of (0, 1] is a constant, and m is the maximum order of the predictor and the corrector. If m = Omega(log n) then both algorithms have O(root nL) iteration complexity. They are superlinearly convergent even for degenerate problems.
Two corrector - predictor interiorpointalgorithms are proposed for solving monotone linear complementarity problems. The algorithms produce a sequence of iterates in the N-infinity(-) neighborhood of the central pat...
详细信息
Two corrector - predictor interiorpointalgorithms are proposed for solving monotone linear complementarity problems. The algorithms produce a sequence of iterates in the N-infinity(-) neighborhood of the central path. The first algorithm uses line search schemes requiring the solution of higher order polynomial equations in one variable, while the line search procedures of the second algorithm can be implemented in O(m n(1+alpha)) arithmetic operations, where n is the dimension of the problems, alpha is an element of (0, 1] is a constant, and m is the maximum order of the predictor and the corrector. If m = Omega(log n) then both algorithms have O(root nL) iteration complexity. They are superlinearly convergent even for degenerate problems.
Meshes containing elements with bad quality can result in poorly conditioned systems of equations that must be solved when using a discretization method, such as the finite-element method, for solving a partial differ...
详细信息
Meshes containing elements with bad quality can result in poorly conditioned systems of equations that must be solved when using a discretization method, such as the finite-element method, for solving a partial differential equation. Moreover, such meshes can lead to poor accuracy in the approximate solution computed. In this paper, we present a nonlinear fractional program that relocates the vertex coordinates of a given mesh to optimize the average element shape quality as measured by the inverse mean-ratio metric. To solve the resulting large-scale optimization problems, we apply an efficient implementation of an inexact Newton algorithm that uses the conjugate gradient method with a block Jacobi preconditioner to compute the direction. We show that the block Jacobi preconditioner is positive definite by proving a general theorem concerning the convexity of fractional functions, applying this result to components of the inverse mean-ratio metric, and showing that each block in the preconditioner is invertible. Numerical results obtained with this special-purpose code on several test meshes are presented and used to quantify the impact on solution time and memory requirements of using a modeling language and general-purpose algorithm to solve these problems.
暂无评论