小波变换在岩石测试中的应用

主要研究了小波变换在岩石超声波测试信号分析中的应用。通过对岩石超声信号的小波分析,提取岩石信号在小波变换下的不同尺度的细节,从而确定出了岩石的节理结构等所对应的信号小波变换细节特征,以及岩石信号在各个不同尺度下的差异,为小波变换在岩石测试中的应用奠定基础。     

小波分析在岩石信号测试中的应用

研究了小波变换在岩石超声波测试信号分析中的应用，通过对岩石信号的小波分析，确定出岩石的裂隙以及完整程度。     

岩石超声波检测信号的小波分析

利用小波变换分析岩石超声检测信号，了解岩石内部结构特性和物理力学特性。建立了岩石超声测试实验系统，并进行多分辨率分析。结果表明，小波分析可以对指定频带和时间段内的信号成分进行分析，在时域和频域具有良好的局部化性质。可以准确地抓住瞬变信号的特性，对频率成分采用逐渐精细的时域或空域取样步长，从而聚焦到信号的任意细节。完整岩石试样超声检测信号及其小波变换波谱比较规则，无复杂变化，但反射波衰减较快，不同岩性的岩石，其超声波检测信号无明显差别，其小波变换却不相同。这差异是由于岩石的细观组构不同造成的。小波变换波谱反映了岩石节理、裂隙等岩石的完整程度。     

小波变换及其在岩石超声检测中的应用

介绍了小波变换的基本概念和特性。应用小波变换对岩石超声波检测信号进行了时频分析和处理。结果表明,该方法是分析处理具有时变谱特性的非平稳信号的一种有效方法。     

岩石测试信号的小波分析

介绍了小波分析的基本方法及其在岩石测试信号分析中的应用。     

小波多重分形及其在岩石爆破振动信号分析中的应用

在说明仅用一种分形维数来描述岩石爆破振动信号不足的基础上,利用多分形分析的方法对典型岩石爆破振动信号的奇异谱进行分析。给出了基于小波变换的多分形谱计算方法,并将此方法应用到岩石爆破振动信号中,讨论了信号的多分形特征,认为信号的突变主要集中在α<1的奇异指数上,而信号的奇异指数也主要集中在0 .2 8～0 .72之间;并提出了对于岩石爆破振动信号几乎处处奇异的结论     

小波变换在岩石断层超声检测中的应用

介绍了小波变换的基本概念及其特性，通过对模拟岩石断层信号的小波处理，提取其频谱特性，从而确定岩石内部的完整性，了解断层结构所对应的波谱特性，为确定岩石的内部结构，了解岩石的内部状况作好预知性工作，为矿山开发等实际生产应用起到参考借鉴作用。通过对岩石断层结构在信号的前三个尺度上的反映，根据样本岩石的结构来确定波谱特征，实践证明该方法十分有效。     

石灰岩声发射频谱特性演化及破裂阶段识别

为获得石灰岩受压破裂阶段声发射识别信息,开展石灰岩单轴压缩声发射试验,获得加载全过程的声发射特征参数及其波形信息,首先结合石灰岩应力与累积能量走势的特征选取 5 个岩石加载破坏过程中的关键点。通过频谱分析与小波包分析,找到石灰岩声发射频谱特征变化规律,获得适合的破裂阶段识别信息;其次利用小波包分解所提取的频带能量占比训练 BP 神经网络,为岩石破裂阶段预警提供双 重保证。研究结果表明：主频值整体呈现先上升后下降的趋势,频谱宽度变化为 200 kHz-300 kHz-200 kHz,频率由单一低频转化为低高频并存后又恢复单一低频;低频高幅为频谱特征的一种主要形态存在;小波包分解将信号频率分为 8 个频段,可将 1、2 低频段之和小于 30%的信号作为特征点,进行岩石破裂预测;以该特征点为界将石灰岩声发射信号划分为两类,训练后的 BP 神经网络能够实现这两类信号的快速准确识别与分类,对于预测岩石破裂阶段有一定价值。     

小波包分析在信号压缩中的应用

着重介绍了将信号在小波包最优基下展开,利用小波包最优基极好的空间、尺度定位性,使得信号的小波包变换系数在小波变换域尽可能集中,从而使在不降低压缩信号的质量情况下,进一步提高信号压缩比成为可能.具体讨论了小波包分析及小波包最优基的选取,同时针对小波分析在信号压缩中的局限性,研究用小波包分析来进行信号的压缩,从而提高了信号的压缩比和重建信号的质量,并用于实际数据处理压缩.     

小波分析及其在弱信号处理中的应用

应用离散小波分析进行数字弱信号分析及特征提取.离散小波分析具有时—频分析特性,能将信号的细微变化反映出来.对实时获取的数字弱信号作离散小波变换分析的结果表明;离散小波分析可明显提高数字信号的信噪比,十分利于从噪声中提取微弱信号.     

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.     

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.     

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-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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