二维三次非线性相位耦合的切片谱分析

针对二维三次非线性相位耦合问题，定义了特殊四阶累积量及相应的四阶累积量切片谱，并利用四阶累积量切片谱方法对二维三次非线性相位耦合进行了分析。利用复数信号的四阶累积量有2^4种定义方式这一特点，分别利用两种特殊的四阶累积量的定义。该方法有效地估计出高斯噪声背景下的参与二维三次非线性相位耦合的谐波频率和耦合产生的谐波频率。从而识别出系统的非线性。仿真实验验证了该算法的有效性。     

二维谐波频率的频域非线性预滤波估计方法

根据谐波信号在带噪信号的频谱中表现为异常脉冲这一特性,提出了一种新的有色噪声背景下二维频率估计方法.利用二维滑动中值滤波器能够滤除异常点的能力,提取噪声频谱,消除有色噪声对信号的影响.将有色噪声转化为白噪声,然后利用高分辨率的二维ESPRIT方法估计信号频率.在不需要知道有色噪声任何统计特性的情况下,该方法对有色噪声具有很强的普适性,仿真实验表明,在信噪比达到-18 dB时,该算法仍然能够准确地估计频率.且由于算法中仅利用了二阶统计量,更便于实现.     

相关乘性和加性噪声背景下的二维谐波恢复

针对乘性噪声和加性噪声均为零均值,且乘性噪声之间相关,乘性噪声和加性噪声之间也相关,这种复杂噪声背景下的二维谐波恢复问题,利用二维循环统计量方法进行了研究.提出了二维噪声互可混的概念,用来体现多个二维噪声之间的相关关系;定义了特殊的二维四阶时间平均多矩谱来估计信号频率.仿真实验证明了算法的有效性.     

二维正弦信号频率估计的ESPRIT方法研究

为了在噪声背景下估计二维正弦信号的频率,并获得较高的估计精度,给出了二维相关阵的大特征值所对应的主特征向量,位于由信号向量张成的信号子空间的结论,并因此提出了一种新的基于最大特征值所对应的第1特征向量的二维谐波频率估计ESPRIT(Estimation of Signal Parameters Via Rotational Invariance Techniques)方法.该方法用此第1特征向量构造一个特殊矩阵代替MEMP(Matrix Enhancement and Matrix Pencil)方法中的数据矩阵,进一步用二维ESPRIT方法来估计谐波频率.该方法依赖于信号子空间,对噪声和数据长度敏感性小,同时它不需进行谱峰搜索,可以得到较高的估计精度.同时给出了较为简便的频率配对算法.仿真实验证明了算法的正确性.     

基于盖氏圆与TAM的电力系统谐波检测

电力系统中谐波检测是无功补偿、谐波滤除等电能质量分析与控制的前提。针对传统电力系统中谐波检测方法存在的问题,结合盖氏圆和TAM算法进行谐波检测。该算法以信号空间为模型,首先用盖氏圆检测出信号源数,然后结合信号子空间和噪声子空间的正交性以及子空间的旋转不变性,估计出信号的频率,最后由全最小二乘法(TLS)计算得到信号的幅值。仿真实验与实际数据分析结果表明:该方法速度快、精确度高,具有一定的应用前景。     

利用高阶统计量恢复二维谐波

基于高阶统计量提出了一种频域恢复频率、时域恢复幅度的时频域相结合的二维谐波信号的恢复方法。该方法由于使用了高阶累积量，因此不再受背景噪声为高斯白噪声的限制，可应用于高斯噪声中二维谐波信号的恢复。仿真实验证明了该方法的可行性     

非平稳噪声环境下LFMCW信号恒虚警检测算法研究

为了提高电子侦查系统中对非平稳噪声环境下线性调频连续波信号的实时检测能力,提出了一种对信号进行分段检测的低复杂度算法.根据假定最大调频斜率设定窗函数宽度,将截获信号均匀分割为多个序列,在每个时间序列内建立短时谐波模型,并采用多个正交窗函数对信号进行加权离散傅里叶变换.在此基础上,推导出符合F分布的检测模型.该模型与噪声功率无关,因此检测前无需统计噪声功率,可对非平稳噪声环境下的信号进行恒虚警率检测.仿真分析了影响该算法性能的参数,通过与单窗口检测算法对比,验证了该算法在非平稳噪声环境下优良的检测性能.      

高精度介质损耗角实时在线测量方法

为提高电气设备介质损耗角的测量精度,利用最优相关滤波法提取基波信号,通过短时傅里叶变换（STFT）插值谐波方法,抑制长频谱泄露的影响。仿真结果表明,最优相关滤波法可以克服加性噪声和调制性噪声的影响,在低信噪比情况下,能够有效消除噪声并检测出有用信号,提高STFT加窗谐波分析法的计算精度。系统频率在49.5～50.5 Hz时,该算法仍能保持较高的计算精度,且受频率变化影响较小。该方法能有效提高信号的分辨能力和准确度。     

复杂噪声中基于累积量的二维DOA估计

针对自相关算法的局限性,研究了复杂环境(乘法与加法观测噪声共存时)中,通过高阶累积量对二维DOA估计的问题.算法能同时确定目标的仰角与方位角;高阶累积量使得算法能够更加有效抑制消除乘法噪声.该方法对任何平稳的加性与乘性噪声均不敏感,因而具有较大的实用性.     

子空间分解法在声目标特征提取中的应用

目的　研究用于识别直升机目标声信号的特征提取方法。方法　通过对直升机声信号频域特性分析,采用基于子空间分解的多重信号分类法(MUSIC)算法提取信号谐波频率作为目标特征,利用子空间分解将观测数据分解为信号子空间与噪声子空间的特点,抑制噪声干扰,提高识别能力。结果与结论　对实测的直升机声信号谐波频率提取结果表明,子空间分解方法提取目标频域特征是可行的,用MUSIC算法提取谐波频率值是有效的。     

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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