基于全相位谱线插值的电力谐波检测方法研究

传统基于FFT的谐波检测方法在非同步采样或非整周期截断情况下会产生严重的频谱泄漏,为抑制频谱泄漏对谐波检测精度的影响,提出基于全相位谱线插值的电力谐波检测新方法.该方法使用全相位谱实际频点附近的三根离散谱线获得频率和幅值校正量,并利用离散全相位谱峰值谱线相位即为对应的实际频率相位的特点,无需另加校正即可实现较高的相位精度.利用全相位谱旁谱线相对于主谱线按平方衰减的特性,并结合旁瓣衰减速度快的Nuttall四项五阶余弦窗,可有效抑制基于FFT谱线插值算法相邻谐波成分的相互干扰,提高谐波检测精度.通过与三谱线插值法和全相位时移相位差法的仿真对比实验,结果表明文中提出的算法具有更好的谐波检测精度.     

基于高阶矩形卷积窗的多频信号参数估计

非同步采样多频信号后,为了减少对信号进行快速傅里叶变换(FFT)而出现的频谱泄漏和栅栏效应等负面影响,设计了一种高阶矩形卷积窗与三谱线插值相结合的信号参数估计方法,推导了多频信号频率、幅值和相位的估计公式,并利用多项式拟合出相应的关系表达式.利用高阶矩形卷积窗+三谱线插值算法、FFT和加Hanning窗算法进行多频信号参数估计对比仿真实验,实验结果表明,对于多频信号的频率和幅值,高阶矩形卷积窗+三谱线插值算法比FFT和加Hanning窗算法的估计精度更高.     

基于全相位FFT三谱线校正的电网谐波与间谐波检测算法

电网谐波检测中,传统FFT算法存在的频谱泄露现象影响了检测的精度.为解决这一问题,分析和比较了全相位FFT算法与FFT算法之间的区别,将一种三谱线校正方法推广到精度更高的全相位FFT算法,并由此提出一种全相位FFT三谱线校正算法.该算法利用频谱峰值频点周围三根谱线信息构造频率偏移量修正公式,进而获得全相位FFT幅值和频率校正值,并利用全相位FFT的相位不变性直接获得信号相位.通过与FFT三谱线插值算法、全相位FFT双谱线校正算法和全相位FFT双谱线插值算法对比,结果表明该全相位算法具有更好的谐波和间谐波检测精度,并且抗白噪声能力更强.     

基于傅立叶分析的非均匀采样信号内插重构方法

针对实际采样过程中出现的采样非均匀性,从随机过程的角度研究非均匀采样信号的谱特性,提出频域均匀抽样傅立叶逆变换的非均匀时域采样信号重构方法。将非均匀采样信号描述为不均匀采样时刻冲激函数代数和的形式,利用傅立叶变换得到非均匀采样信号的频谱曲线,由采样时刻随机均匀分布的特点,得到反应原信号频谱特性的非均匀采样信号频谱数学期望,再由频域抽样理论重构原信号。MATLAB仿真实验验证了这种非均匀采样信号分析与重构方法的正确性,将这一研究成果应用到机械抖动激光陀螺输出信号处理中,得到了可靠的符合实际的机械正弦抖动幅频曲线并重构出激光陀螺正弦抖动机构的输出信号。     

结合数字滤波技术的随机共振弱信号检测

应用数值计算研究强噪声背景下弱信号的随机共振检测. 探讨了大频率条件下非线性双稳态系统随机共振的输出信号幅值、 信噪比与随机噪声的关系, 数值计算结果表明, 非线性双稳态系统对大频率噪声具有较大的压制特性, 通过随机共振系统可以检测强噪声背景下的大频率弱信号. 结合数字滤波技术提取了大频率弱信号, 并获得被检测大频率弱信号的特征频率谱线及时域图像.      

实时混合模拟频域评价方法的物理意义

为研究实时混合模拟频域评价方法的物理意义,通过数值模拟和实验室试验,分别计算了线性结构和非线性结构在整个试验以及各个频率下的幅值、相位(时滞)和权重.研究发现,各频率上的幅值、等效时滞按照权重加权可以得到整个试验的幅值、等效时滞.因此,实时混合模拟频域评价方法的物理意义实际上是计算各个频率上的幅值和相位(时滞),并根据输入信号各个频率幅值平方的权重进行加权得到试验的幅值和相位(时滞).由于权重的影响,频域评价结果受输入中低频成分的控制;对于非线性结构,需注意虚假时滞对计算结果的影响.     

基于正弦模型的汉语普通话语音分析合成方法

针对PSOLA算法会引起语音频谱的不连续,从而影响合成语音的质量,提出了一种基于正弦模型的汉语普通话语音基音同步分析和合成算法.首先,将连续的语音信号在时间轴上分为一帧帧短时信号,再把每一帧短时语音信号分解为一系列不同幅值、相位和频率的正弦分量,然后根据频率匹配的原则,对相邻两帧信号的幅度和相位进行插值,得到合成信号的正弦分量的幅值和相位,最后将各正弦分量相加,就得到了合成的语音信号.实验结果证明,该方法合成的语音信号的各个正弦波分量的相位和幅值均能平滑过渡,从而可以克服PSOLA算法带来的回声效应,有助于提高合成语音的自然度.     

基于Nuttall自卷积窗四谱线插值FFT的电力谐波分析方法

快速傅里叶变换(fast Fourier transform,FFT)在非同步采样条件下难以实现谐波的高精度检测,而加窗和插值算法可以提高谐波检测的准确度。文章在分析Nuttall自卷积窗频谱特性的基础上,提出了基于Nuttall自卷积窗四谱线插值FFT算法。该算法通过对加窗信号离散频点处幅值的分析,利用谐波频点附近的四根谱线进行加权运算,进一步提高谐波幅值、相位和频率检测的精度;采用多项式拟合的方式得到基于Nuttall自卷积窗四谱线插值修正公式。仿真数据表明,该算法具有较高的谐波检测精度,Nuttall自卷积窗有效地抑制了频谱泄露。     

准同期参数测量算法研究

在发电机并网过程中,对信号的频率、相位、幅值等参数要进行快速、准确的测量,传统的测量方法参数误差比较大.本文提出利用窗函数及频谱校正的DFT算法来对信号进行参数测量,仿真结果表明,该算法不需要对电压信号进行整周期采样,可以对频率在较大范围内变化的信号进行准确测量,从而较好的解决了由于并列双方电压的频率不断变化而引起的测量误差大的问题.     

频谱泄漏效应补偿的信号处理方法研究

为减小频谱泄漏对谱分析的影响, 将传统离散傅里叶变换(DFT: Discrete Fourier Transform)的方法和运算从经典的一维频谱扩展到二维时频谱, 在此基础上对简谐信号存在能量泄漏的频谱中任意频率成分的幅值与时域信号截断长度的关系(时谱)进行实验研究, 从而提出一种信号的时谱描述方法。实验结果表明, 在频谱泄漏条件下任意频率成分的幅值随时域信号截断长度的变化遵从sinc 函数, 基于这种关系可完成简谐信号任意截断条件下的频谱构造, 实现零误差幅值谱构成, 得到非整周期截断时DFT 幅值谱误差与信号中所含周期数的关系服从指数规律, 且当信号长度是周期的10 倍时, DFT 频谱产生的标准差约为0. 001。     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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