基于EMD的前后置滤波语音增强算法

针对低信噪比下语音增强困难的问题及经验模态分解(empirical mode decomposition,EMD)在语音增强中的有效应用,提出了一种基于EMD的前后置滤波语音增强算法.将含噪语音信号进行卡尔曼滤波后做EMD分解,采用能量阈值法判断出含有残余噪声的本征模态函数(IMF),对其小波变换后与其余IMF重构为最终的语音增强信号.实验表明,在输入信噪比为-10~5dB的不同噪声环境下,以时域分段信噪比及语音质量感知评测PESQ作为评价指标,效果均优于单独的EMD、小波软阈值法及卡尔曼滤波算法,是一种有效的语音增强算法.     

基于经验模态分解空域相关滤波的脉冲星信号消噪

针对脉冲星信号信噪比极低,且信号中有色噪声成分远大于高斯白噪声的特点,提出了一种基于经验模态分解(empirical mode decomposition,EMD)的脉冲星信号空域相关滤波消噪方法。首先建立脉冲星信号的分形高斯噪声模型,根据双对数功率谱密度估计分形高斯噪声的Hurst参数值;然后,结合脉冲星累积信号的窗口辐射特性和分形高斯噪声经EMD分解后的噪声分布特点,估计脉冲星信号各层内蕴模态函数(intrinsic mode function,IMF)中噪声的方差;最后,以IMF噪声方差为基础,建立EMD空域相关滤波方法并应用于脉冲星累积轮廓消噪。实验结果表明,与经典的平移不变小波阈值消噪法、平移不变小波空域相关滤波消噪法以及EMD模态单元比例萎缩消噪法相比,改进的EMD空域相关滤波消噪法在抑制脉冲信号中的噪声和保留更多的微脉冲特征细节信息方面更加有效。     

基于经验模态分解的齿轮箱故障特征提取

利用小波去噪阈值法对齿轮箱故障振动信号进行去噪,将经验模态分解(EMD)和快速傅里叶变换(FFT)相结合对齿轮箱故障进行特征提取,此方法适合于对非线性非稳态信号进行自适应的分析.利用小波阈值去噪方法对原始信号进行预处理,将去噪后的信号进行经验模态分解,得到一定数量的本征模态函数(IMF)分量,选取特定的IMF进行FFT,得到相应的功率谱,从而达到提取齿轮箱故障特征频率的目的.对齿轮箱故障信号进行分析,结果表明该方法能够有效地识别出齿轮箱故障特征频率.     

基于改进EMD的麦克风阵列语音增强研究

提出一种将改进EMD与麦克风阵列MVDR自适应波束形成相结合的语音增强方法。该方法利用互相关系数阈值法去除将EMD算法分解后的的虚假IMF分量,结合各阶IMF分量的自相关函数特性准确获取信号与噪声的主导IMF分量分界点,然后对所有噪声主导的IMF分量进行小波阈值去噪,接着将所有剩余IMF分量进行MVDR波束形成获得增强语音信号。改进EMD算法避免了在高信噪比条件下的信号失真,与MVDR波束形成相结合,满足了MVDR窄带特性要求,增强了麦克风阵列抗干扰能力。实验结果证明了方法的有效性。     

液压挖掘机反铲切削过程振动信号去噪处理

针对小波包频带能量分解和Hilbert-Huang变化在信号的去噪研究中的优势,对比2种方法在液压挖掘机反铲切削过程中振动信号去噪的准确度.以液压挖掘机工作装置的振动信号为例,利用小波包频带能量分解算法与Hilbert-Huang变化算法分别对振动信号进行重构.其中,Hilbert-Huang变换首先是对振动信号通过经验模态分解(empirical mode decomposition,EMD)得到IMF分量;然后,对IMF分量进行Hilbert谱分析,得到IMF分量的能量特征,选择有用的IMF分量进行信号重构,从而消除噪音信号的干扰.研究结果表明:与小波包频带能量分解方法相比, Hilbert-Huang变换的液压挖掘机反铲切削过程振动的重构信号更加接近真实信号.     

基于小波EMD的柴油机油耗量测量信号去噪处理

提出基于小波经验模态分解的柴油机油耗量信号去噪处理算法.将柴油机油耗量测量信号进行经验模态分解(EMD)后,经阈值处理和尺度滤波,去掉主要干扰因素所对应的本征模函数(IMF)分量,然后对剩余IMF分量进行重构,得到去噪后柴油机油耗量测量信号的时间序列.测试结果表明:重构后的信号能反映柴油机油耗量信号的真实趋势,其相对误差约为0.72％.     

基于MEEMD和二代小波阈值的表面肌电信号去噪处理

表面肌电(surface electromyogram, sEMG)信号能够反映神经肌肉的相关活动信息,被广泛应用于假肢控制、临床医学等领域,而获取干净的sEMG信号是精确地解释和应用信号的先决条件。为了消除混杂在sEMG信号中的噪声,文章提出了一种基于改进的经验模态分解(modified ensemble empirical mode decomposition, MEEMD)与二代小波改进阈值函数相结合的sEMG信号去噪方法。对含噪的sEMG信号进行MEEMD分解,再对高频的本证模态分量(intrinsic mode function, IMF)进行二代小波改进阈值函数去噪,将处理后的高频IMF分量和低频IMF分量以及残余信号进行重构,重构后的信号即为去噪sEMG信号。仿真结果表明,基于MEEMD与二代小波改进阈值函数方法的去噪性能指标高于其他方法;实验结果表明,该方法结合了MEEMD和二代小波的优点,能够很好地消除噪声,且能最大限度地保留信号中的有用信息。     

基于经验模态分解的核磁共振去噪方法研究

核磁共振（NMR）在孔隙结构评估和流体识别方面具有独特的优势，但NMR信号很容易受到噪声影响。根据NMR噪声的时域和频域特征，提出了基于一种经验模态分解（EMD）的NMR去噪方法。首先，利用EMD将信号由高频到低频分解为一系列的本征模态函数，以此分解噪声和噪声NMR信号，然后，使用曲线趋势法和改进的过零点率曲线确定信号噪声分离准则，将有用信号叠加到剩余项以获得去噪信号。通过岩芯数据和测井数据对比发现，基于EMD的去噪方法可以提高信噪比的同时保留孔隙结构信息，其去噪效果优于小波阈值和EMD小波阈值法，计算得到的孔隙度接近实际孔隙度。     

基于EMD的基音检测预处理技术

针对基音检测的性能严重受背景噪声影响的问题,论文基于经验模态分解(EMD)理论,研究了含噪语音信号的EMD分解特性,参照小波阈值去噪方法,提出了一种基于EMD的自适应语音去噪算法,并且针对软、硬阈值函数的不足提出了一种新的阈值函数.MATLAB仿真结果表明,该方法可以有效地去除噪声,较好地恢复语音信号,与小波阈值去噪方法相比,信噪比、均方根误差等性能指标均有明显提高.     

改进EMD在轴承故障诊断中的应用

为解决传统镜像延拓经验模态分解(mirror Empirical Mode Decomposition,简称mirror-EMD)在对信号分解过程中易受随机噪声干扰,易产生虚假固有模态分量(Intrinsic Mode Function,简称IMF)的缺点,论文提出了一种将自适应小波阈值去噪,镜像延拓EMD分解,相关系数法剔除虚假IMF三者相结合的改进EMD方法 (简称wt-mirror-EMD).该方法首先对原始故障信号去噪,然后对去噪后信号镜像延拓EMD分解,得到若干个IMF分量,最后对各IMF分量计算相关系数,对相关系数大的主IMF作频谱分析。仿真信号和实际轴承信号分析均表明,wt-mirror-EMD,该方法相对于传统改进mirror-EMD方法,尤其是当有噪声干扰时,检测结果更加准确。     

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

正~~