Solution to impedance distribution in electrical impedance tomography （EIT） is an ill-posed nonlinear inverse problem. It is especially difficult to reconstruct an EIT image in the center area of a measured object. ...Solution to impedance distribution in electrical impedance tomography （EIT） is an ill-posed nonlinear inverse problem. It is especially difficult to reconstruct an EIT image in the center area of a measured object. Tikhonov regularization with some prior information is a sound regnlarization method for static electrical impedance tomography under the condition that some true impedance distribution information is known a priori. This paper presents a direct search method （DSM） as pretreatment of image reconstruction through which one not only can construct a regularization matrix which may locate in areas of impedance change, but also can obtain an initial impedance distribution more similar to the true impedance distribution, as well as better current modes which can better distinguish the initial distribution and the true distribution. Simulation results indicate that, by using DSM, resolution in the center area of the measured object can be improved significantly.展开更多
Three PRP-type direct search methods for unconstrained optimization are presented. The methods adopt three kinds of recently developed descent conjugate gradient methods and the idea of frame-based direct search metho...Three PRP-type direct search methods for unconstrained optimization are presented. The methods adopt three kinds of recently developed descent conjugate gradient methods and the idea of frame-based direct search method. Global convergence is shown for continuously differentiable functions. Data profile and performance profile are adopted to analyze the numerical experiments and the results show that the proposed methods are effective.展开更多
In this paper, we propose a new separable fractional interpolation model which can be established by 2n interpolation points where n is the number of variables. Based on this model, a new direct search method is prese...In this paper, we propose a new separable fractional interpolation model which can be established by 2n interpolation points where n is the number of variables. Based on this model, a new direct search method is presented. In this method, a new iterate is determined by solving the fractional interpolation model in trust region. Under mild assumptions, the convergence results of this method are given and proved, Numerical experiments show that the new method is promising.展开更多
In this paper, an alternating direction nonmonotone approximate Newton algorithm (ADNAN) based on nonmonotone line search is developed for solving inverse problems. It is shown that ADNAN converges to a solution of th...In this paper, an alternating direction nonmonotone approximate Newton algorithm (ADNAN) based on nonmonotone line search is developed for solving inverse problems. It is shown that ADNAN converges to a solution of the inverse problems and numerical results provide the effectiveness of the proposed algorithm.展开更多
提出了一种混合演化算法求解多目标优化问题.演化算法是解决多目标优化问题的有效方法,在全局优化问题中具有很好的鲁棒性,但其局部搜索性能有待改善.Hooke and Jeeves方法是一经典的局部搜索算法,将其与演化算法结合求解多目标优化问题...提出了一种混合演化算法求解多目标优化问题.演化算法是解决多目标优化问题的有效方法,在全局优化问题中具有很好的鲁棒性,但其局部搜索性能有待改善.Hooke and Jeeves方法是一经典的局部搜索算法,将其与演化算法结合求解多目标优化问题,提高了解的收敛质量,因而从整体上提高了算法的性能,并且测试结果也说明了该算法的可行性.展开更多
文摘Solution to impedance distribution in electrical impedance tomography （EIT） is an ill-posed nonlinear inverse problem. It is especially difficult to reconstruct an EIT image in the center area of a measured object. Tikhonov regularization with some prior information is a sound regnlarization method for static electrical impedance tomography under the condition that some true impedance distribution information is known a priori. This paper presents a direct search method （DSM） as pretreatment of image reconstruction through which one not only can construct a regularization matrix which may locate in areas of impedance change, but also can obtain an initial impedance distribution more similar to the true impedance distribution, as well as better current modes which can better distinguish the initial distribution and the true distribution. Simulation results indicate that, by using DSM, resolution in the center area of the measured object can be improved significantly.
文摘Three PRP-type direct search methods for unconstrained optimization are presented. The methods adopt three kinds of recently developed descent conjugate gradient methods and the idea of frame-based direct search method. Global convergence is shown for continuously differentiable functions. Data profile and performance profile are adopted to analyze the numerical experiments and the results show that the proposed methods are effective.
基金Supported by the National Natural Science Foundation of China(Nos.11071117 and 11001128)ChinaRussia(NSFC RFBR)Cooperation Program(No.11211120155)
文摘In this paper, we propose a new separable fractional interpolation model which can be established by 2n interpolation points where n is the number of variables. Based on this model, a new direct search method is presented. In this method, a new iterate is determined by solving the fractional interpolation model in trust region. Under mild assumptions, the convergence results of this method are given and proved, Numerical experiments show that the new method is promising.
文摘In this paper, an alternating direction nonmonotone approximate Newton algorithm (ADNAN) based on nonmonotone line search is developed for solving inverse problems. It is shown that ADNAN converges to a solution of the inverse problems and numerical results provide the effectiveness of the proposed algorithm.
文摘提出了一种混合演化算法求解多目标优化问题.演化算法是解决多目标优化问题的有效方法,在全局优化问题中具有很好的鲁棒性,但其局部搜索性能有待改善.Hooke and Jeeves方法是一经典的局部搜索算法,将其与演化算法结合求解多目标优化问题,提高了解的收敛质量,因而从整体上提高了算法的性能,并且测试结果也说明了该算法的可行性.
文摘本文针对整数梯度搜索方向的局部性以及有时因取整而方向发散的缺点,提出了在离散设计空间中,利用离散坐标邻域点的目标函数值信息和适当的延伸探索直接构造离散搜索方向,并进行离散一维搜索的寻优方法,对此称之为离散直接搜索法(A Discrete Direct Search Method),简称DDSM法。本文运用DDSM法成功地解决了14个工程考题和数学考题,实践表明:DDSM法的求解速度和可靠性比较令人满意,尤其是计算效率相对现有的某些离散优化方法有较明显的提高。
