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1.
对称四阶偏微分方程去噪算法   总被引:4,自引:1,他引:3       下载免费PDF全文
陈波  张立伟 《计算机工程》2008,34(13):188-189
通过分析整体变分模型的去噪原理和效果,提出一个新的四阶偏微分方程去噪模型,用于克服二阶偏微分方程去噪后使图像分块的缺点,同时保持去噪后图像的高保真性,并发展一个基于四邻域系统的对称离散化算法用于求解新模型,应用中值滤波去除四阶偏微分方程去噪所引起的亮点。实验结果表明,与传统方法相比,以该算法去噪后的图像具有更好的质量和视觉效果。  相似文献   

2.
将前向后向扩散系数引入到You和Kaveh提出的四阶偏微分方程去噪模型中,前向扩散用于对噪声进行平滑,后向扩散则对图像特征进行强化.同时,改进了模型中拉普拉斯算子的离散形式,使其包含更多的图像信息,能够更准确的判断图像的特征.新方法处理后的图像,避免了二阶偏微分方程处理图像常出现的"阶梯"效应,同时,和同类的四阶偏微分方程去噪模型相比,该方法的处理结果不会出现"斑"点,因此视觉效果更加理想.最后,通过实验证明了该方法的有效性.  相似文献   

3.
PDE模型在声纳图像去噪中的应用研究   总被引:1,自引:0,他引:1  
偏微分方程方法在光学图像去噪中已有很多成功的应用,但用于声纳图像去噪的情况还不多见。针对声纳图像受噪声污染严重的问题,将偏微分方程原理引入到声纳图像去噪中,重点讨论了两种偏微分方程模型:ROF模型和四阶扩散模型。基于这两种模型对声纳图像进行去噪处理,仿真实验证明了偏微分方程去噪算法的有效性,并对比分析了两种模型的去噪性能。ROF模型适用于低信噪比条件下的声纳图像处理,而四阶扩散模型在高信噪比条件下,能够很好地保持图像边缘,但当噪声污染严重时,其去噪后的SNR比ROF模型去噪低了近10 dB,不利于声纳图像处理。  相似文献   

4.
一种改进的PDE图像去噪方法   总被引:2,自引:0,他引:2       下载免费PDF全文
研究用于图像去噪的偏微分方程;在理论上对去噪原理进行了分析。通过对扩散方程中扩散系数的改进,提出了一个对噪声图像更有效、更具有适应性的去噪扩散模型,对高斯噪声图像进行处理。与传统的各向异性扩散算法进行了比较并对偏微分方程的未来发展方向进行了展望。实验结果表明,该方法在有效去除噪声的同时较好地保留了图像中的重要细节信息,使图像的细节部分清晰。该方法可以有效地去除图像噪声,提高图像的质量。  相似文献   

5.
陈凤 《计算机工程与设计》2007,28(16):4055-4058
针对具有线性纹理特征的图像,对基于偏微分方程的一致增强性扩散去噪方法进行了研究,详细分析了它的扩散去噪过程和纹理结构的保护及增强,设计出具体的算法步骤.在此基础上,针对线性结构图像序列,给出了三维一致增强性扩散模型.在选择合适的扩散参数情况下,一致增强性扩散算法不但使具有线性结构图像的信噪比有明显的提高,而且可以很好的保护和增强线性结构,具有广泛的应用领域.  相似文献   

6.
Curvelet去噪彻底,易产生“阶梯”效应,四阶偏微分方程LLT模型去噪能很好地保护图像细节特征,不会产生阶梯效应。提出了一个模型将Curvelet去噪和四阶偏微分方程中LLT模型去噪的优点通过权函数λ结合起来,实验表明,新的模型能很好地发挥二者的优点,不但很好地保护图像细节特征,消除阶梯效应,去噪彻底且能很好地保持边缘,去噪率和视觉效果优于Curvelet和LLT方法。  相似文献   

7.
谢美华  王正明 《计算机应用》2005,25(5):1078-1080
讨论了图像去噪的扩散方程模型中所存在的最优停止时间选取问题。通过对图像点乘一个与梯度成反比的作用系数来构造一个新的去噪后的图像与去掉的噪声之间的相关系数,最优停止时间的选取就等价于极小化该相关系数。该准则能有效抑制图像中高频信息的存在对相关系数计算的影响,获得准确的最优停止时间,并无需预先知道图像中的噪声水平。仿真计算结果表明采用该准则所得的停止时间非常接近于基于最优峰值信噪比所得的停止时间,且广泛适用于各种噪声水平。  相似文献   

8.
基于拓扑导数的复扩散在图像去噪及边缘提取中的应用   总被引:1,自引:0,他引:1  
提出了基于拓扑导数的非线性复扩散用于图像去噪及边缘提取的一种算法.由于线性扩散会使图像边缘模糊,基于拓扑优化思想,对每个像素点的线性复扩散系数扰动,使得拓扑导数最小的扩散系数为最优.文中选取的扩散系数具有各向异性的特性,从而克服了Perona-Malik的各向同性扩散系数不利于去除边缘噪声的缺陷,选择拓扑导数足够小的像素点,对这些像素点用最优扩散系数进行扩散.文中给出了使算法迭代终止的判据.实验证明,与Guy Gilboa的非线性复扩散相比,本文方法对原始加噪图像处理后,实部图像体现出了更好的去噪效果,虚部图像则很好地保留了图像边缘,此外,本文方法还消除了Perona-Malik的方法对图像去噪后产生的阶梯效应.  相似文献   

9.
随着激光技术的发展,激光光斑检测在实际应用中越来越广泛,但激光的远距离传输易受环境噪声的影响从而导致光斑检测误差变大。因此,以激光光斑为研究对象,针对激光光斑图像去噪这一重要问题,进行了改进算法研究。首先针对传统四阶偏微分方程去噪模型存在边缘模糊和自适应差的问题,从扩散函数的角度出发并根据不同光照下光斑的检测参数引进自适应梯度阈值,提出一种改进四阶偏微分方程去噪模型;其次将所提模型应用于雪天、雾天和雨天不同光照条件下激光光斑去噪中去;最后分别与基于自适应梯度阈值的各向异性去噪模型(IPM)、统一变分模型(DC)和ML四阶PDE去噪模型进行对比分析,结果表明所提算法不仅使去噪后的光斑图像内部保持平滑、边界保持清晰,且对不同光照条件具有较高的自适应性。  相似文献   

10.
针对全变分及四阶偏微分方程图像去噪模型的不足,利用小波变换能够聚焦到图像细微变化的优势,提出一种基于小波域的偏微分方程图像去噪算法。并通过对小波的阈值和阈值函数做适当的改进以及利用加权函数将全变分和四阶偏微分方程去噪模型相结合的方法,得到一种改进的小波域耦合偏微分方程图像去噪模型。MATLAB仿真结果表明,该模型和小波软阈值去噪、全变分模型以及四阶偏微分方程图像去噪模型相比,峰值信噪比有明显的提高,而且能够在很好地保留图像的边缘和细节信息的同时提高处理噪声的效率。  相似文献   

11.
基于偏微分方程的各种非线性图像平滑模型, 可归结为求解初始值为输入图像的非线性扩散方程. 这些非线性图像平滑模型在滤除噪声的同时, 在保留图像重要特征方面表现出良好的性能.采用这些模型对图像进行平滑的过程中,迭代停止准则对图像平滑的效果有着重要的影响.该文提出了一种简单实用的最优停止准则,该准则确定了一个标准,使得平滑后的图像与噪声的相关性最小时停止迭代. 它易于实现而且又有很强的通用性.实验结果表明该算法可以在图像平滑过程中适时地停止迭代, 获得满意的图像平滑效果.  相似文献   

12.
以随机分析的知识和最优控制理论为基础,推广了一类带停时的奇异型随机控制中的折扣费用模型,主要在受控状态过程中增加了漂移因子和扩散因子,使其为一随机微分方程的解,并将费用函数一般化.通过求解一组变分方程,证明了最优控制及最优停时的存在性,并给出了最优费用函数的解析表达式.  相似文献   

13.
In this paper we introduce and solve the partially observed optimal stopping non-linear risk-sensitive stochastic control problem for discrete-time non-linear systems. The presented results are closely related to previous results for finite horizon partially observed risk-sensitive stochastic control problem. An information state approach is used and a new (three-way) separation principle established that leads to a forward dynamic programming equation and a backward dynamic programming inequality equation (both infinite dimensional). A verification theorem is given that establishes the optimal control and optimal stopping time. The risk-neutral optimal stopping stochastic control problem is also discussed.  相似文献   

14.
A model reduction technique—the Proper Generalized Decomposition (PGD) for solving time dependent and multidimensional parameters is reviewed and applied to both the Fisher-type equations and the heat equation. Space-time discretization and separated representation technique for obtaining fast convergence computation while maintaining real time is detailed. Three situations of the Fisher-type equation are solved by the PGD and the results show a perfect agreement with the exact solutions. The source term of the heat equation is given a Huxley source and the thermal diffusivity is taken to be linearly dependent of the spatial parameter. The results show how the Fisher-type equation finds application to the heat equation and that the PGD method allows a perfect representation of the temperature distribution defined in a 5-D tensorial product space and time.  相似文献   

15.
Optimal portfolios with regime switching and value-at-risk constraint   总被引:1,自引:0,他引:1  
We consider the optimal portfolio selection problem subject to a maximum value-at-Risk (MVaR) constraint when the price dynamics of the risky asset are governed by a Markov-modulated geometric Brownian motion (GBM). Here, the market parameters including the market interest rate of a bank account, the appreciation rate and the volatility of the risky asset switch over time according to a continuous-time Markov chain, whose states are interpreted as the states of an economy. The MVaR is defined as the maximum value of the VaRs of the portfolio in a short time duration over different states of the chain. We formulate the problem as a constrained utility maximization problem over a finite time horizon. By utilizing the dynamic programming principle, we shall first derive a regime-switching Hamilton-Jacobi-Bellman (HJB) equation and then a system of coupled HJB equations. We shall employ an efficient numerical method to solve the system of coupled HJB equations for the optimal constrained portfolio. We shall provide numerical results for the sensitivity analysis of the optimal portfolio, the optimal consumption and the VaR level with respect to model parameters. These results are also used to investigating the effect of the switching regimes.  相似文献   

16.
The usual (non-stochastic stopping) control problem is extended to the case of random terminal time. The more general model presented hero should be particularly useful when a system will change while being controlled. Systems which are otherwise deterministic, and systems with additive noise in the dynamic equation are considered.

Results concerning the relevant aspects of reliability and Markov process theories are presented. We show that stochastically stopped control optimality conditions are simply extensions of the usual conditions and that the limits of the criteria and optimal control, as the variance of the stopping probability distribution approaches zero, are the corresponding quantities for the non-stochastic problem.  相似文献   

17.
The selection of stopping time (i.e., scale) significantly affects the performance of anisotropic diffusion filter for image denoising. This paper designs a Markov random field (MRF) scale selection model, which selects scales for image segments, then the denoised image is the composition of segments at their optimal scales in the scale space. Firstly, statistics-based scale selection criteria are proposed for image segments. Then we design a scale selection energy function in the MRF framework by considering the scale coherence between neighboring segments. A segment-based noise estimation algorithm is also developed to estimate the noise statistics efficiently. Experiments show that the performance of MRF scale selection model is much better than the previous global scale selection schemes. Combined with this scale selection model, the anisotropic diffusion filter is comparable to or even outperform the state-of-the-art denoising methods in performance.  相似文献   

18.
针对移动云计算中虚拟机迁移过程的性能优化问题,提出了一种基于最优停止理论的预拷贝传输策略。该策略通过最优停止理论对寻找最优传输速率的最优停止模型求解,从而获得最优传输速率,由此来减少虚拟机迁移过程中的迁移数据总量和总时间。在仿真实验中,将所提出的传输策略与相关文献的传输策略进行对比,给出不同传输策略的性能结果分析。实验结果表明,所提出的策略具有较少的迁移数据总量和总时间,能有效地提高迁移过程的性能。  相似文献   

19.
This paper deals with the optimal stopping problem for multiarmed bandit processes. Under the assumption of independence of arms we show that optimal strategies and stopping times are expressed by the dynamic allocation indices for each arm. This paper reduces this problem to several independent one-parameter optimal stopping problems. On the basis of these results, we characterize optimal strategies and stopping times. Moreover, this paper also extends those to the case allowing time constraints. In the case where arm's state evolve according to Markov chains with finite state, linear programming calculation of optimal strategies and stopping times is discussed.  相似文献   

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