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基于无噪后验错误矢量信号能量的变正则因子仿射投影算法  [PDF]
师黎明,林云
电子学报 , 2015, DOI: 10.3969/j.issn.0372-2112.2015.01.002
Abstract: 变正则因子技术是提高仿射投影自适应算法性能的重要方法之一.由于环境噪声的影响,现有的变正则因子自适应算法收敛速度较慢且稳态误差较大,各种测量、评估误差的存在进一步恶化了算法性能.为提高自适应算法的跟踪性能,本文在分析无噪先验错误矢量、无噪后验错误矢量和额外均方错误间关系的基础上,提出通过最小化无噪后验错误矢量信号能量来推导自适应变正则因子表达式的方法.在实践应用中,该方法利用了测量噪声的统计方差特性,并提出一种更加光滑且更加容易控制的指数缩放因子评估方法.系统辨识的仿真结果表明本文方法与传统的变正则因子方法以及变步长方法相比有更快的收敛速度与更低的稳态误差.
分布式传感器网络中基于条件后验克拉美-罗下界的被动声目标跟踪局部节点选择算法
CPCRLB based local node selection for passive acoustic target tracking in a distributed sensor network
 [PDF]

江潇潇,赵晓丽,金婕,邓琛
- , 2018, DOI: 10.16300/j.cnki.1000-3630.2018.05.005
Abstract: 针对分布式传感器网络下的被动声目标跟踪问题,提出了一种基于条件后验克拉美罗下界(Conditional Posterior Cramér-Rao Lower Bounds,CPCRLB)的局部传感器节点选择算法,基于被动声探测背景下的纯方位量测数据,采用粒子滤波器推导得到了CPCRLB的近似解析表达式,进而在该CPCRLB的基础上定义了节点效用贡献作为节点选择准则,结合分布式传感器网络的特点提出了一种局部节点选择方法,节点需知道全网传感器节点的信息,而是仅利用局部节点信息来决定下一时刻节点的活动状态,从而在实现自治节点选择的同时大大减少网络通信量。通过仿真结果表明,该算法在跟踪精度、能量消耗和计算复杂度方面都表现出较好的性能。
For passive acoustic target tracking in a distributed sensor network, this paper proposed a local node selection algorithm based on conditional posterior Cramér-Rao lower bounds (CPCRLB). The approximate analytical expression of CPCRLB is derived by utilizing particle filters for bearing-only measurements, and it is used to define the utility contribution as the node selection criterion. In the proposed algorithm, each node can only use the local information to determine whether to be activated without the knowledge of all nodes in the network. Simulation results prove the effectiveness of our method and show good performance in tracking accuracy, energy consumption and computational complexity.
Maximum a posteriori filtering for synthetic aperture radar images based on heavy-tailed Rayleigh distribution of speckle
基于斑点噪声的拖尾Rayleigh分布的合成孔径雷达图像最大后验概率降噪

Sun Zeng-Guo,Han Chong-Zhao,
孙增国
,韩崇昭

物理学报 , 2007,
Abstract: In order to reflect the statistics of high peak and heavy tail,speckle in synthetic aperture radar images is modeled as heavy-tailed Rayleigh distribution.First,based on Gamma prior distribution and heavy-tailed Rayleigh distribution of speckle,the maximum a posteriori filtering equation is proposed and its analytical form is provided in given characteristic parameter.Second,parameters of heavy-tailed Rayleigh distribution are estimated from the observed image using Mellin transformation.Last,maximum a posteriori de-speckling experiments and their quantitative measures are given.In order to eliminate the influence of window size and noise intensity on de-speckling results,dynamic relations of the de-speckling capability to noise variance and window size are suggested respectively.Results demonstrate that the heavy-tailed Rayleigh distribution accords with the real statistics of speckle,so the maximum a posteriori filter in heavy-tailed Rayleigh distribution of speckle has higher capability of noise reduction compared to the one in Rayleigh distribution of speckle and the Kuan filter.
基于二次对数能量熵小波包的母猪哺乳声去噪方法研究  [PDF]
闫丽,沈明霞,刘龙申,孙昕,姚文,徐亚妮
农业机械学报 , 2015, DOI: 10.6041/j.issn.1000-1298.2015.11.045
Abstract: 以小梅山母猪发出的哺乳呼噜声及其它干扰噪声为研究对象,利用噪声能量在频域内均匀分布,其对应的信息熵值最大的特性,根据噪声类型不同,选择不同小波包层数结合信息熵计算,去除环境噪声混叠的影响。试验结果表明,母猪呼噜声的频率范围在0~800Hz内,仔猪争乳尖叫声的频率大于1000Hz,其他干扰噪声的频率范围0~8000Hz内;分别经过5层和3层的db10小波包分解,利用对数能量熵软阈值去除0~8000Hz主噪声及1000~8000Hz内的残留噪声,且重构信号中母猪哺乳声的波形特征保持较好,获得令人满意的滤波处理结果,为进一步研究畜舍环境下母猪哺乳声音特征提取及识别提供了数据预处理方法。
城市绿化的声衰减  [PDF]
程明昆,柯豪
环境科学学报 , 1982,
Abstract: 本文试图通过对北京地区的不同绿化结构声衰减的测量和分析,找出减噪效果较好的绿化结构形式。从各种绿化结构的声衰减结果可以看到绿篱、乔灌木和草坪构成的绿带效果较好,平均可以减噪5dB(A)。
Mesoscopic Speckle  [PDF]
Sheng Zhang,Yitzchak Lockerman,Azriel Z. Genack
Physics , 2009, DOI: 10.1103/PhysRevE.82.051114
Abstract: We have measured the local and global statistics of singularity velocity, v, and have related these through the spatial correlation function of v. The distribution of v is a mixture of a mesoscopic distribution of global change in the speckle pattern and the distribution for v for Gaussian random fields. When v is normalized by the standard deviation of the fractional intensity change, probability distributions and correlation function of v approach those for random Gaussian fields. These results are directly analogous to the statistics of transmitted intensity normalized by the total transmission and provide a unified framework for understanding statistics of speckle evolution and intensity.
Speckle interferometry  [PDF]
S. K. Saha
Physics , 1999,
Abstract: We have presented the basic mathematical treatment of interferometry in the optical domain. Its applications in astronomical observations using both the single aperture, as well as the diluted apertures are described in detail. We have also described about the shortcomings of this technique in the presence of Earth's atmosphere. A short descriptions of the atmospheric turbulence and its effect on the flat wavefront from a stellar source is given. The formation of speckle which acts as carrier of information is defined. Laboratory experiments with phase modulation screens, as well as the resultant intensity distributions due to point source are demonstrated. The experimental method to freeze the speckles, as well as data processing techniques for both Fourier modulus and Fourier phase are described. We have also discussed the technique of the aperture synthesis using non-redundant aperture masks at the pupil plane of the telescope, emphasizing set on the comparison with speckle interferometry. The various methods of image restoration and their comparisons are also discussed. Finally, we have touched upon certain astrophysical problems which can be tackled with the newly developed speckle interferometer using the 2.34 meter Vainu Bappu Telescope (VBT), situated at the Vainu Bappu Observatory (VBO), Kavalur, India.
Speckle Reduction in Ultrasound Image
M. Saranya,C. Saraswathy
International Journal of Electronics and Computer Science Engineering , 2012,
Abstract: In this paper, a detailed description and comparison of speckle reduction of medical ultrasound is presented. Four speckle reduction filters are described in a detailed fashion to facilitate implementation for research and evaluation. The filtering techniques considered include Lee,Kuan,Frost and Oriented Speckle Reducing Anisotropic Diffusion(OSRAD). These filtering techniques are applied to a 2D liver image and respective de speckled images are obtained. Application of objective quality metrics quantifies the preservation of image edges, overall image distortion, and improvement in image contrast. It is concluded that the optimal method is the OSRAD diffusion filter. This method is capable of strong speckle suppression with less computational complexity.
Tailoring PDC speckle structure  [PDF]
G. Brida,M. Genovese,A. Meda,I. Ruo-Berchera,E. Predazzi
Physics , 2008,
Abstract: Speckle structure of parametric down conversion light has recently received a large attention due to relevance in view of applications to quantum imaging The possibility of tailoring the speckle size by acting on the pump properties is an interesting tool for the applications to quantum imaging and in particular to the detection of weak object under shot-noise limit. Here we present a systematic detailed experimental study of the speckle structure produced in type II PDC with particular attention to its variation with pump beam properties.
Singularities in Speckled Speckle: Screening  [PDF]
David A. Kessler,Isaac Freund
Physics , 2008, DOI: 10.1364/JOSAA.25.002932
Abstract: We study screening of optical singularities in random optical fields with two widely different length scales. We call the speckle patterns generated by such fields speckled speckle, because the major speckle spots in the pattern are themselves highly speckled. We study combinations of fields whose components exhibit short- and long-range correlations, and find unusual forms of screening.
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