基于小波包熵的船舶轴频电场信号消噪研究

在海洋环境下,为有效地将微弱的轴频电场信号提取出来,本文在对小波包熵理论分析的基础上,提出了基于小波包熵的船舶轴频电场信号消噪方法.首先使用小波包变换对测量信号进行多子带分解,并将各子带分成几个子区间;然后计算各子带不同子区间的小波包熵,利用最大小波包熵自适应地选择各子带的阈值;最后对各子带的小波包系数进行阈值处理,并利用处理后的小波包系数对信号进行重构.通过实测数据和仿真数据对该消噪方法进行验证,结果表明此方法在低信噪比情况下能较好地将微弱的轴频电场信号从环境背景噪声中分离出来.     

保密通信新介质--人工神经网络

根据人工神经网络的结构特点和信息传输与处理特征，提出了利用物理神经网络作为通信信道的观点．在分析了现有通信信道物理模型之后，具体讨论了作为通信信道的神经网络的可能拓朴结构、神经网络学习要点、允许传输信号的模式特征，研究了神经网络信道的传输延时、通信带宽及信噪比，分析了神经网络信道处理多媒体信号的计算潜力，并着重剖析了神经网络信道固有的保密通信特征．最后给出了一个具体的神经网络信道设计实例．     

小波分析和神经网络在过程数据预处理中的应用

分析了信号的奇异性检测原理,利用小波变换模极大值在多尺度上的表现与李普西兹指数间的关系,对小波变换后的系数进行处理,重构小波变换,然后对重构后的小波变换进行小波反变换,达到信号预处理的目的;同时,介绍了自联想网络的结构及其在信号消噪方面的应用.仿真实例表明,利用这2种方法进行过程数据的预处理,消噪后信号的信噪比显著提高;小波变换模极大值方法具有很理想的逼近精度,而神经网络则具有快速的计算能力.     

基于Matlab的小波消噪技术仿真与实现

信号处理技术中有一项重要的技术就是信号噪声的消除,利用小波对噪声信号进行分解,通过消噪阈值对小波系数进行处理、重构后得出小波消噪后的信号。在计算机上利用Matlab软件上进行仿真测试,结果表明,选取不同的小波可以得到不同的消噪信号结果,通过阈值的调整能得到较好的消噪结果。     

基于小波神经网络的振动信号消噪

论文在介绍小波神经网络结构和算法的基础上,给出对振动信号消噪的实例。文中采用正交的Shannon小波函数作为小波元,进行数字仿真信号消噪实验和实测信号消噪实验,实验结果表明用小波神经网络对振动信号进行消噪是一种有效的方法。     

心电信号小波分析

心电信号是一种非平稳并具有很多奇异点的微弱信号。小波变换中的模极大值消噪法具有非线性及自适应性,小波的这种特性对于类似于心电信号这种非平稳微弱信号是十分适用的。针对传统的消噪方法在处理心电信号时的局限性,研究了小波变换的时-频局部化特性及基于多分辨率分析的信号小波分解和重构算法———Mallat算法。采用小波分析的模极大值法实现对QRS波R峰值点的检测,以及对心电信号的消噪处理。通过试验研究可知,运用小波进行QRS波检测,QRS波的识别率高达99.9%,经过消噪重构后的心电信号信噪比较原始信号有较大提高。     

应用小波变换进行信号消噪处理

小波分析在时域与频域同时具有良好的局部化性质,可以利用信息信号和噪声信号在小波变换下具有截然不同的奇异性来区分信息信号与噪声信号。根据信号与噪声在二进制小波变换随尺度参数减小时信息信号和白噪声信号的小波变换的模极大值点变化的不同性质做消噪处理,然后再重建消噪后的信号。采用本研究所给出的方法对实际数据进行处理,其结果表明应用小波分析可以明显地抑制噪声,提高信噪比。此方法具有很好的实用价值。     

信号消噪的小波处理方法及Matlab实现

通过对噪声特性的分析，并应用小波的方法对信号进行消噪处理，利用Matlab软件演示信号消噪的效果，总结出小波分析对信号消噪的优点。     

小波在信号消噪处理中的应用

利用正交样条小波对信号进行消噪处理，并与其他常用的小波如Daubeches小波作了比较．实验表明，利用正交样条小波进行信号消噪处理可得到很好的效果．     

基于离散小波变换门限消噪法阈值确定的研究

本文利用信号和噪声表现出截然不同的特性,在原有软／硬阈值消噪的基础上提出了最大似然估计闽值消噪法。结果表明,利用小波变换进行消噪处理,最大似然估计闽值法优于正交小波变换中的软／硬阈值处理,在均方差较小的情况下信噪比得以提高。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to