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唐俊 《中国新技术新产品》2011,(20):144-145
电力系统状态估计是能量管理系统(EMS)的重要组成部分,其结果直接影响电网调度的智能化分析与决策。综述了电力系统状态估计的研究现状。首先,简要分析了电力系统经典静态状态估计和动态状态估计的基本功能及其发展;然后,介绍了几种目前新出现的状态估计方法,即新息图状态估计、谐波状态估计、配电网状态估计等,指出各个方法的优缺点。最后,对状态估计方法中值得研究的方面进行了展望。 相似文献
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阐述了基于时延估计的阵形估计方法的基本原理,该方法比基于传感器测量和基于匹配场处理的方法具有更强的适应性和较高的精度.对比分析了单辅助信源和双辅助信源的相应的阵形估计方法,其中单信源方法用装配间距近似各个阵元间的实际间距.对已有海试数据阵形估计处理的结果表明,阵列弯曲不大时,单源方法可以得到与双源方法相当精度的估计结果,用估计阵形进行空间谱分析,进一步说明了结果的有效性.基于时延估计的阵形估计方法对长水听器阵列的应用及阵形估计具有较大应用价值. 相似文献
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周兆经 《中国计量学院学报》1993,(2)
本文论述了非平稳信号瞬时频率(IF)的估计方法,包括基干最小均方误差(LMS)算法或递推最小二乘(RLS)算法的自适应IF估计方法和基于信号相位多项式模型的IF估计方法。对各种估计方法的估计方差与理论方差下限进行了比较。说明了,基于互Wigner分布的估计方法所需信噪比(SNR)门限值最低。在低SNR、短信号记录的情况下,用多项式相位模型与最大似然法可以获得比较可靠的IF估计。 相似文献
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几种基于FFT的频率估计方法精度分析 总被引:31,自引:0,他引:31
介绍了噪声背景中正弦信号频率估计的方差下限,对利用FFT主瓣内两条幅度最大谱线进行插值的频率估计方法(Rife-Jane方法和Quinn方法)以及利用FFT相位进行频率插值的方法(分段FFT相位差法和重叠FFT相位差法)的方差进行了理论分析,推导了Quinn方法的频率估计方差计算公式.提出了通过滤波进一步提高分段FFT相位差法的频率估计精度的方法。通过计算机MonteCarlo模拟实验对上述各种方法的频率估计精度以及加窗函数的影响进行了分析并与理论下限进行了比较,指出了每种方法所能达到的估计精度。 相似文献
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用核估计的方法,构造了自回归模型AR(p)的参数的一种经验Bayes(EB)估计,证明了这种估计的渐近最优性。模拟计算表明,该估计不仅优于古典估计方法,也优于现有的EB估计方法 相似文献
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阵形估计是水听器阵列应用中的关键问题,基于时延估计的阵形估计方法比基于传感器测量和基于匹配场处理的方法具有更强的适应性和较高的精度。针对浅海水听器阵列中水平长线阵存在的纵向相关振荡现象引起的不能简单以某一阵元为基准求相对时延的问题,充分利用了阵元信号的高相关性,提出了基于子阵时延的阵形估计方法,针对子阵间时延估计误差向阵端累积的问题,该方法以时延估计的克拉美罗界为依据提出了合理的子阵方式,在一定程度上减小了误差传递。对已有海试数据阵形估计处理的结果表明,相对于单源固定间距方法和未分子阵的双源时延估计方法,基于子阵时延的阵形估计方法满足阵元间距的约束,有较好的空间谱特性,减小了阵形估计误差,对长水听器阵列的应用及阵形估计具有较大应用价值。 相似文献
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描述芯片或电力系统运行规律的常用数学模型是高维微分代数方程组,其中的微分方程组太大,线性多步法和Runge-Kutta法等经典数值方法均不能有效求解。为求解这些微分方程组,借鉴常微分方程经典数值方法的A稳定定义,提出了波形松弛方法A稳定(强A稳定),给出了基于θ方法的波形松弛方法 A稳定(强A稳定)和非A稳定的条件,以及几个支持理论结果的数值算例。研究结果表明WR方法并非天然继承底层方法的A稳定性,为使波形松弛方法 A稳定,需要使用A稳定的底层方法和适当的分裂函数,这为刚性方程WR方法的构造奠定了理论基础。此外,借鉴经典数值方法的B稳定定义,提出了波形松弛方法的B稳定(强B稳定),给出了波形松弛方法强B稳定的条件。 相似文献
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Design methods have been studied by researchers for decades. Academia considers their impact on industry to be insufficient.
The objective of this research is to understand the use and impact of design methods in the context of a specific company,
Volvo Car Corporation (VCC), by describing the behaviour of engineers in relation to methods, to assist in the future development
of design methods and tools. We mainly concentrate on concept selection methods because of their relevance in this company.
The data presented is the result of qualitative research carried out during 4 years at VCC, where the authors were located
as researchers. The research shows that many methods are employed besides those with an academic name, that some in-company
methods used contain improvements to methods researched by academia, that some modifications to academic methods lead to unreliable
results, and that there is a lack of objectivity in method modification. For these reasons, the authors suggest further research
on understanding the principles of successful and unreliable modification of concept selection methods. 相似文献
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Michael D. McKay 《Reliability Engineering & System Safety》1997,57(3):267-279
This paper examines the feasibility and value of using nonparametric variance-based methods to supplement parametric regression methods for uncertainty analysis of computer models. It shows from theoretical considerations how the usual linear regression methods are a particular case within the general framework of variance-based methods. Examples of strengths and weaknesses of the methods are demonstrated analytically and numerically in an example. The paper shows that relaxation of linearity assumptions in nonparametric variance-based methods comes at the cost of additional computer runs. 相似文献
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M. Papadrakakis 《International journal for numerical methods in engineering》1982,18(12):1785-1799
A state-of-the-art survey of a family of vector iterative methods with three-term recursion formulae is presented. The methods can be classified under two broad categories. The Chebyshev semi-iterative type of methods and the conjugate gradient type of methods. Relationships between the iteration parameters of the methods are established and computational techniques for estimating these parameters are presented. Numerical tests confirm the superiority of the conjugate gradient method for linear problems and the Chebyshev semi-iterative methods for nonlinear problems. 相似文献
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A summary of the results of an extensive comparative experimental study of Fourier transformation and model-fitting methods of spectral analysis of random time-series data is presented. It is illustrated that Fourier transformation methods can be an essential companion to model-fitting methods even for short data segments with underlying sharp spectral peaks. The best spectrum estimates can be obtained by taking advantage of the strengths of both types of methods. For example, it is shown that detection and estimation of the frequencies of spectral lines for short data segments can be best accomplished using certain parametric methods in conjunction with Fourier transformation methods to aid in model-order selection and identification of spurious peaks in the parametric spectrum estimate, and that estimation of amplitude and phase for sine-wave removal, given frequency estimates, and spectrum estimation after sine-wave removal can often be best accomplished with Fourier transformation methods alone. 相似文献
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V. T. Troshchenko 《Strength of Materials》2010,42(3):241-257
We review the currently available methods that are used to explain the difference in fatigue strength of metals and alloys
under conditions of uniform and nonuniform stressed states. We discuss (i) the empirical methods, (ii) the methods allowing
for the difference between nominal and effective cyclic stresses, (iii) the methods based on the notions of statistical theories
of strength, and (iv) the methods assuming that responsible for fatigue failure are the averaged stresses in the surface layer.
The calculated results are verified against experimental findings. 相似文献
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Jan Langer Marian Klasztorny Salah El-Sayed El-Bagalaty' 《International journal for numerical methods in engineering》1992,33(5):889-905
The paper presents a family of methods with postintegration, for numerical integration of non-linear dynamic equations of motion of discrete systems. Both explicit and implicit algorithms of these methods are conditionally stable, but can give solutions of accuracy of a few orders higher than the known methods with preintegration, corresponding to them. A general analysis of stability and accuracy of single-step methods is carried out. The postintegration methods have been tested on a single-degree-of-freedom non-linear system. 相似文献
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本文介绍了七种测定P-S-N曲线的方法。并且用五种材料的实验数据对上述测定方法作了分析比较。在比较了几种方法的优缺点的基础上,提出了选择试验方法的建议和结论。 相似文献