基于独立分量分析的声发射信号去噪方法

针对声发射信号比较微弱,实际检测信号中常含有强背景噪声的问题,提出了基于独立分量分析(ICA)的信号去噪方法.该方法首先对观测信号进行FastICA分解,得出多导独立分量;再根据一定的时域及频域先验知识,将独立分量中的噪声信号通道置零,利用解混矩阵反演出去噪后的信号.文中通过断铅声模拟发射信号去噪仿真和埋地水管泄漏声发射信号去噪实验,对该方法进行定性和定量分析.结果表明,与常规的去噪方法比较,ICA去噪方法受噪声强度影响较小,能够得到更高的信噪比和更好的相关系数,有利于提高埋地水管泄漏点的定位精度.     

ICA特征提取技术在背景噪声建模与分析中的应用

应用infomax学习规则对船舶辐射噪声信号进行独立成分分析(ICA)特征提取,并证明了ICA变换能增强信号的非高斯性.在此基础上,根据稀疏编码的特性,利用阈值化的方法将船舶辐射噪声信号有效去噪.通过对含有海洋环境噪声的船舶辐射噪声信号的去噪实验,证明了本方法的有效性,并且去噪结果明显优于传统的几种去噪方法.     

基于分形维数的刀具状态在线监测新方法

以分形几何理论为基础,对刀具不同磨损阶段声发射信号的分形特征进行了分析。提出了计算非完全分形体信号波形的关联维数时尺度范围的确定方法,分析了声发射信号在刀具磨缶过程中分形维数的变化特性。刀具磨损切削实验数据表明,声发射信号的分形维数受切削参数变化影响较小,分形维数反映了声发射信号的几何特征,其大小能较好地反映刀具的不同磨损状态。实验结果表明,该方法能正确地实时在线监测刀具的不同磨损状态。     

刀具压入破岩声发射分形特征实验

选用一字型刀具对花岗岩进行静力破碎实验,采用AEwin-USB型声发射信号采集系统采集声发射信号,应用分形理论分析不同加载速率下声发射分形特性.结果表明,随着加载速率的增加,刀具破岩程度愈显剧烈,且伴随着的声发射信号更强;声发射振铃计数率、能量率曲线能够很好描述刀具破岩过程;刀具破岩过程中声发射参数序列具有分形特征,且分形维数随加载速率的增大而逐渐减小;声发射分形维数随时间变化规律很好地反映了刀具破岩是一个降维有序、耗散结构的过程;刀具破岩声发射序列分维曲线呈一个波动上升→持续降低直到最低的变化规律,可以将分形维数持续降低作为岩石破坏失稳的前兆依据.     

级联双稳随机共振降噪下的有噪ICA研究

研究了强噪声混合条件下的独立分量分析（ICA）问题．提出了一种将级联双稳随机共振（SR）用于有噪ICA盲源分离的方法．该方法利用级联双稳SR对时域波形降噪的优良特性，先对有噪ICA信号进行SR输出，再进行ICA盲源分离．实验结果表明，利用上述方法可以有效提高有噪ICA的分离效果．     

独立分量分析在单一信号中的去噪问题

多源激励情况下,从传感器阵列输出的高维响应中分离、识别不同振源的性质,对于大型结构振动分析及其状态监测与健康评价有着重要的意义.传统的去噪方法都存在信号的失真问题,从信号的独立性出发,采用ICA分离噪声信号,保证了信号的真实性,针对单一信号进行仿真,证实了ICA去噪的有效性.     

一种基于ICA的机械缺陷超声信号提取方法

针对强噪声背景下缺陷超声回波信号检测的问题,利用了基于独立分量分析的方法进行缺陷信号的提取。该方法首先对观测信号进行JADE分解,得出多导独立分量,再根据赫斯特指数,分离缺陷信号和噪声信号。通过对仿真和实测缺陷超声信号的去噪实验研究,结果表明,与小波去噪方法相比,ICA去噪方法能够得到很好的信噪比,有利于强噪声背景下缺陷的去噪处理及微弱信号的提取。     

基于声发射的塔吊安全检测方法与实验研究

针对现有的塔吊安全检测技术存在抗干扰能力差,实时性不足的问题。提出一种基于声发射的塔吊安全检测方法。通过详细分析声发射波源在吊塔缺陷区域形成的信号特征,引入小波去噪技术去除检测中的电气干扰噪声、机械噪声、传播途径引起的畸变和衰减等干扰。运用参数分析和波形分析两种技术,识别缺陷区域信号特征。仿真实验结果表明,基于声发射的塔吊安全检测方法能够较好地去除干扰,采集到稳健性较好的去噪特征信号,对塔吊非安全区域的连续型和突变型损伤特征信号能较好地重构,满足应用需求。     

LMD和改进小波阈值去噪的轴承声发射信号故障诊断

针对机械故障声发射信号特征提取的问题,提出了一种局部均值分解(local mean decomposition,LMD)和改进的小波阈值去噪相结合的方法;并应用于滚动轴承的故障诊断。首先,把改进小波阈值与三种小波阈值去噪方法进行比较分析。通过仿真信号表明,改进小波阈值方法能更为有效地去除噪声。其次,采用LMD方法将原始轴承故障的声发射信号分解,分解为若干个乘积函数(production function,PF)的线性组合,通过相关系数原则选取能够反映故障特征的PF分量,利用改进小波阈值去噪法对选出的PF分量进行进一步去噪。最后,对去噪后的声发射信号进行包络谱分析,诊断轴承故障的位置。通过滚动轴承单一故障和耦合故障的声发射实验验证了该方法的有效性。     

含噪ICA模型的一种时频算法

实际ICA(Independent Component Analysis)模型中,观测信号常常被各种噪声干扰,致使ICA的源估计相当困难.针对信号源噪声污染情形,分析了ICA模型的估计难点;并假设信号和噪声的时频特性不同,以一种高性能的双线性时频分布计算混合信号的时频特性,辅之Hough空间变换思想,将噪声能量扩展到整个参数空间,只选择信号能量占主导的自项点进行最小二乘对角化估计源信号,提出了一种时频抗噪ICA方法;最后,详细分析了该方法的抗噪性能.该方法扩展了ICA模型的应用限制条件,能有效分离各种非平稳信号.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

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.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

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

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.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-