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131.
On a nonlinear multigrid algorithm with primal relaxation for the image total variation minimisation
Digital image restoration has drawn much attention in the recent years and a lot of research has been done on effective variational partial differential equation models and their theoretical studies. However there remains an urgent need to develop fast and robust iterative solvers, as the underlying problem sizes are large. This paper proposes a fast multigrid method using primal relaxations. The basic primal relaxation is known to get stuck at a ‘local’ non-stationary minimum of the solution, which is usually believed to be ‘non-smooth’. Our idea is to utilize coarse level corrections, overcoming the deadlock of a basic primal relaxation scheme. A further refinement is to allow non-regular coarse levels to correct the solution, which helps to improve the multilevel method. Numerical experiments on both 1D and 2D images are presented. 相似文献
132.
In the present paper, we study the rate of convergence in simultaneous approximation for the Bézier variant of the Baskakov-Beta operators by using the decomposition technique of functions of bounded variation. 相似文献
133.
Ole E. Barndorff-Nielsen Neil Shephard Matthias Winkel 《Stochastic Processes and their Applications》2006
In this paper we provide a systematic study of how the probability limit and central limit theorem for realised multipower variation changes when we add finite activity and infinite activity jump processes to an underlying Brownian semimartingale. 相似文献
134.
135.
针对传统鲨鱼优化算法在求解高维目标函数时,易早熟收敛,陷入局部最优的缺陷.提出一种基于正弦控制因子的Lateral变异鲨鱼优化算法.通过正弦曲线的特性和自适应惯性权重,改善了传统鲨鱼优化算法中由于随机选取控制因子数值大小可能导致算法在迭代后期全局搜索能力降低的问题,提高了算法在迭代后期的全局收敛能力,并对最佳鲨鱼位置引入Lateral变异策略,加强了算法跳出局部最优的可能性.改进后的算法对多个shifted单峰,多峰以及固定维测试函数进行求解,实验结果表明,对比多种不同优化算法而言,本文所提LSSO算法具有更高的收敛精度和搜索速度. 相似文献
136.
Trapti Neer Ana Maria Acu P.N. Agrawal 《Mathematical Methods in the Applied Sciences》2020,43(6):2911-2923
In this paper, we define the Baskakov-Durrmeyer type operators based on generalized Appell polynomials. Here, we establish moment estimates, an estimate via weighted modulus of continuity and a Voronovoskaya type asymptotic result. Further, we study a quantitative-Voronovoskaya-type theorem and Grüss Voronovskaya-type theorem. Lastly, we give the approximation result for functions having derivatives of bounded variation. 相似文献
137.
Richard Greiner Oliver Roth 《Proceedings of the American Mathematical Society》2001,129(12):3657-3664
We consider the linear functional for on the set of normalized univalent functions in the unit disk and use the result to disprove a conjecture of Bombieri.
138.
The problem of estimating of the law
(in the space
of the paths) and the common marginal distribution for a strictly stationary ergodic process X is discussed. We show, in particular, that:(1) The empirical measure
with probability 1 converges weakly in
to
.(2) The empirical measure
corresponding to the path
, converges a.s. when T in total variation to the marginal law if and only if the local time for X exists. (3) The L
p-convergence of the empirical densities f
T to the marginal one is studied.(4) A version of the CLT for empirical densities f
T provided both the mixing properties and the local time of the underlying process are good enough is given. 相似文献
139.
Boris I. Kvasov 《Numerical Algorithms》2001,27(2):169-188
This paper addresses the definition and the study of discrete generalized splines. Discrete generalized splines are continuous piecewise defined functions which meet some smoothness conditions for the first and second divided differences at the knots. They provide a generalization both of smooth generalized splines and of the classical discrete cubic splines. Completely general configurations for steps in divided differences are considered. Direct algorithms are proposed for constructing discrete generalized splines and discrete generalized B-splines (discrete GB-splines for short). Explicit formulae and recurrence relations are obtained for discrete GB-splines. Properties of discrete GB-splines and their series are studied. It is shown that discrete GB-splines form weak Chebyshev systems and that series of discrete GB-splines have a variation diminishing property. 相似文献
140.
Suppose that { f(n), n N
0
} is a sequence of positive real numbers and suppose that the sequence { a(n), n N
0
} is given by a(0) = 0, and, for n 1, by the convolution equation nf(n) = a* f(n). The resulting sequence is denoted by a(n) =
f
(n) and is called the De Pril transform of { f(n), n N
0
} . In this paper, we consider first- and second-order asymptotic behavior of {
f
(n), n N
0
} for a large class of subexponential sequences { f(n), n N
0
} . We also discuss some applications. 相似文献