Estimating respiratory frequency from autoregressive spectral analysis of heart period

In this article we report the results of a pilot study and a larger investigation that examined the relationship between respiration frequency assessed using the traditional mercury strain gauge and using the central frequency of the HF component derived from autoregressive spectral analysis.     

基于线性相关分析的周期自回归短期负荷预测

对配电系统短期负荷预测的周期自回归模型和配电负荷的周期性进行了研究.采用相关分析法对配电负荷的周期特性作了深入地分析,研究结果表明配电负荷的日周期性比周周期性更明显;基于配电负荷的时刻相关性分析,挑选出对预测结果起决定性作用的特征输入量,据此提出了改进的配电负荷日周期PAR预测模型.实例研究表明,该模型较常规PAR预测模型的预测速度更快、精度更高.     

Real‐time spectral analysis

For signal analysis, the Fourier transform and the linear prediction methods are the main approaches. In recent years, the wavelet transform, which gives an expression in the time–frequency domain, has been attracting attention. In the wavelet transform, scale and shift operations are used to analyze regional waves in the signal. In this paper, we propose a new method for signal analysis. Instead of the wavelet, short sine waves and cosine waves which have slightly different frequencies and phases established beforehand are used. These frequencies and phases play the same role as wavelets in analyzing regional waves in the signal. However, our proposed method is different from the wavelet transform because it does not use multiresolution analysis. In conventional spectral analysis methods, all data are prepared beforehand and calculations are performed by using these data. In the proposed method, the spectrum is updated whenever new signal data come in. We show that the amount of calculation is markedly reduced and that real‐time spectral analysis can be achieved. Finally, we present an analysis of Japanese vocal sounds using the proposed method. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 43–50, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20504     

基于功率从属性追踪的购电节点成本分析

为准确分析电网实际运行中每个购电节点的成本盈亏情况,提出了一种基于功率从属性追踪的购电节点成本分析方法.该方法在分析电网功率从属性分布的基础上,构建了电网络功率从属性追踪模型,确定了负荷功率中各电源提供功率的份额;其次采用了一种公平合理的经济准则作为描述能量传输过程中能量损耗引起的经济利益变化的依据,即节点费用守恒原则.该方法可以直接得出购电节点购电成本与负荷节点售电电力成本的解析表达式.最后,通过IEEE9节点算例,验证了该方法对电力市场条件下的购电节点成本分析具有实际应用意义.     

基于功率从属性追踪的购电节点成本分析

为准确分析电网实际运行中每个购电节点的成本盈亏情况,提出了一种基于功率从属性追踪的购电节点成本分析方法。该方法在分析电网功率从属性分布的基础上,构建了电网络功率从属性追踪模型,确定了负荷功率中各电源提供功率的份额;其次采用了一种公平合理的经济准则作为描述能量传输过程中能量损耗引起的经济利益变化的依据,即节点费用守恒原则。该方法可以直接得出购电节点购电成本与负荷节点售电电力成本的解析表达式。最后,通过IEEE9节点算例,验证了该方法对电力市场条件下的购电节点成本分析具有实际应用意义。     

基于网络依存关系的CPPS连锁故障分析及风险评估

信息系统的融合给电网安全运行带来了新的风险，因此有必要研究电力信息物理系统(cyber-physical power system, CPPS)连锁故障的产生及传播机理。首先建立CPPS部分相互依存模型，采用老化因素、潮流、隐性故障、偶然因素构建电网风险元，采用信息占用率、拓扑结构、网络攻击、节点负荷以及依存关系构建信息网风险元，从而将风险元理论应用于CPPS连锁故障预测过程。其次提出一种同时考虑两网失负荷率的风险计算方法，可以识别骨干层与接入层的关键节点。最后分析信息节点自身故障和网络攻击引起的信息节点失效对连锁故障的不同影响。算例分析表明：依存关系会促进故障在两网传播，增大系统的风险；对CPPS进行整体分析能较全面地评估连锁故障风险，识别关键信息节点；同时遭受网络攻击与信息节点自身故障的CPPS的平均风险最高，需采取措施提高其可靠性。     

Nonlinear, non-stationary analysis of interarea oscillations via Hilbert spectral analysis

Hilbert spectral analysis (HSA) is used to characterize the time evolution of non-stationary power system oscillations following large perturbations. Using an analytical procedure based on the Hilbert-Huang Technique (HHT), data from transient stability simulations are decomposed into a finite number of time-varying oscillating components that can be associated with different time scales. Hilbert analysis is then utilized to characterize the time evolution of critical components giving rise to the observed oscillations. The objectives of this study are to obtain information of a quantitative nature on nonlinear processes in power system oscillatory phenomena and assess the applicability of the developed procedures to track the evolving dynamics of critical system modes. A six-area, 377-machine power system is analyzed to examine the onset of nonlinear, non-stationary behavior. Examples of the developed procedures to detect and quantify the strength of nonlinear interaction in power system behavior and to estimate the distribution of the non-stationarity are provided.     

The optimization of spectral analysis for signal harmonics

FFT has been applied to technologies of spectrum analysis widely. However, since the signal sampling is at random, and FFT suffers specific restrictions, some defects inevitably occur, which means that harmonic parameters do not show on the spectrum exactly. These defects result from frequency scales not matching signal characteristics. This paper discusses the optimization of spectrum analysis for signal harmonics. By means of scale fine-tuning, the frequency scales will match the signal characteristics. The method eliminates both of the picket-fence effect and the leakage effect; it makes the harmonic parameters show on the spectrum more accurately. This paper takes reasonable and practical evaluations to verify the theory     

基于非对称阿基米德Copula的多变量水文干旱联合概率研究

推导了5种常用3维非对称阿基米德Copulas函数的条件Copulas和密度函数,阐述了这类Copulas函数研究水文干旱特性联合分布的应用技术问题。以渭河流域北洛河状头站的径流序列为例,干旱变量的边际分布参数分别采用矩法、概率权重法、极大似然法和遗传算法进行计算和选优,并进行了分布函数拟合度检验。变量相依性的度量表明干旱变量间有较强的相依性;根据AIC,BIC和RMSE准则,M12 Copula拟合效果最优。最后,进行了M12 Copula的拟合度检验,计算了北洛河状头站3维水文干旱变量组合的联合概率、条件概率和相应的重现期。     

一种多元LDPC-CPM优化方法及性能仿真分析

为了解决二元低密度奇偶校验(LDPC)码与高阶连续相位调制(CPM)级联的系统在卫星通信、深空通信方面传输性能不足的问题,提出了一种多元LDPC-CPM优化方法。首先采用多元LDPC码与高阶CPM串行级联形成多元LDPC-CPM系统获取更好的传输误码性能。其次考虑到多元LDPC码的传统译码算法复杂度过高,难以硬件实现的问题,设计了一种改进型的Mixed-Log-FFT-BP算法,通过去除加法与查表运算中对数似然比的求解,降低译码复杂度。最后针对多元LDPC-CPM系统涉及参数过多问题,提出一种性能逐步收敛的参数优化方法。仿真结果表明,与优化前的系统相比,优化后的系统在中高信噪比下,误码性能有1～1.2 dB的提升,且系统复杂度较低。     

海浪信号的实时仿真和谱估计

针对海浪信号的随机不确定性问题,依据长峰波海浪理论,给出了海浪信号的数学模型,提出了一种海浪信号的实时仿真方法.采用波能谱(海浪谱)描述海浪的统计特性,采用海浪反演的线性叠加法在Matlab仿真平台上实时仿真出不规则长峰波海浪;利用加矩形窗口的Welch谱估计法对仿真出的海浪做了谱估计,同时与真实谱进行比较.结果表明,该海浪信号的仿真方法既能满足实时仿真的要求,又具有较高的仿真精确度.船舶减摇控制的应用证明,该方法能为船舶运动控制仿真系统提供可靠的海浪扰动信号.     

A test of homogeneity for autoregressive processes

In this paper, we introduce a new hypothesis test to determine whether or not two spectral densities are proportional. We deliberately limit our study to autoregressive processes and derive the asymptotic behaviour of the test. A test for autoregressive coefficient nullity or randomness is deduced. We derive asymptotic behaviour for these tests and show the usefulness of our test to detect speech in a noisy environment. Copyright © 2002 John Wiley & Sons, Ltd.     

Hybrid spatial‐spectral MoM analysis of microstrip structures

In this paper, a new hybrid method formulation to resolve the mixed potential integral equation in an efficient and a fast approach, which is based on a simultaneous formulation in both spatial and spectral domains, is proposed. The entries of the method of moments matrix are then given by the sum of two integrals. The first one is expressed in the spatial domain. This part is analytically evaluated after a development in Taylor series of the exponential terms in the function to integrate. The integrals expressed in the spectral domain have a finite range, and they are calculated using numerical integration. Then the convergence problem is avoided in this approach. A good agreement between the simulated and measured results has been achieved. Copyright © 2015 John Wiley & Sons, Ltd.     

A high-resolution spectral analysis algorithm for power-system disturbance monitoring

In a previous paper, the author presented a Fourier-based algorithm for monitoring the characteristics of the damped oscillating "modes" which are set up after a disturbance in an electric power-distribution system. This earlier paper permitted the analysis of multiple modes but only if the modes were sufficiently well separated to be resolved with conventional Fourier techniques. This current paper extends the previous work to enable the processing of multiple modes which are very closely spaced in frequency. Importantly, the proposed algorithm has good noise performance. A theoretical justification for the new method is presented, and simulations are provided to confirm the theory. The scheme is also tested on a real power-system example.     

Functional relaxations and spectral techniques in Computer-Aided circuit analysis

Analysis of transients in integrated circuits is performed with the use of highly specialized computer programs. The transient responses are computed using time-marching integration methods and require a substantial amount of computer time. A new method based on spectral analysis and waveform relaxation is proposed. The method results in a substantial saving in computing time without compromising the accuracy. A basic algorithm utilizing the spectral technique in a relaxation framework is described. A prototype simulator based on the algorithm was developed and used to simulate certain types of CMOS circuits. The results showed a significant time savings in comparison with the widely used circuit simulator ‘SPICE’. Example circuits and relevant results are provided.     

MLKF谱估计在地基噪声特性分析中的应用

在测试高精度惯性元件时,为了精确地分析地基干扰的噪声特性,针对某实验室地基的振动试验,建立了含有白噪声、指数相关噪声、趋势项、随机游走和地基固有频率的噪声模型,依据极大似然和Kalman滤波理论,推导了一种通过迭代算法调整被估计参数直至收敛的谱估计方法(MLKF).通过仿真算例,验证了该方法的可辨识性和快速逼近性.从具...     

基于谱聚类分析的托辊故障诊断

有效地诊断托辊故障,对提高选煤工作效率和工厂智能化水平具有重要的作用。针对工业现场环境复杂,噪音类型多且杂的特点,首先提出利用差分法来消除托辊音频序列数据时间趋势影响的有效方法,在此基础上提取托辊音频序列特征,分别利用K-Means和谱聚类算法进行聚类分析以及故障识别,并从噪音音频序列数据中挖掘有用的信息。然后为了评价聚类模型的优劣,创新提出将同一音频序列分割得到子音频序列的相同聚类标签的平均比率,以此作为聚类优劣的评判标准。实验结果表明,谱聚类算法的效果优于K-Means,动态选取谱聚类的参数值能够提高局部诊断准确率,且具有较强的鲁棒性,能够实现对生产范围内多种类型噪音音频信号进行有效聚类识别。智能化托辊故障诊断系统的应用提高了选煤工作效率,减少了非计划停机次数,产生了较好的经济效益。     

基于多元特征分析的居民非侵入式相似电器辨识算法

在面向居民的非侵入式负荷辨识场景中,存在部分电路结构、功率相近的相似电器。对于这些电器,现有算法辨识成功率较低。为提高对居民相似电器辨识的准确率,提出了一种基于多元特征分析的非侵入式相似电器辨识算法。该算法使用一对多维的低频电器特征数据进行分析,先将特征规范化,计算两种电器特征间马哈拉诺比斯距离,用以判断两种电器是否相似,再对原始特征使用主成分分析,以提取相似电器的主特征,最后将主特征输入多元高斯模型,得到辨识结果,判断电器运行状态,并分项计量电器能耗。使用实测电器数据与居民实际用电数据进行验证,并与其他模型进行对比。结果显示,该算法可有效提高相似电器辨识的准确性。     

基于频谱细化与插值法的特征谐波分析研究

快速傅里叶变换(fast Fourier transform,FFT)是目前常用的特征谐波分析方法,由于受到栅栏效应和频谱泄漏的影响,其分析精度并不理想。针对特征谐波各项参数的精确估计问题,提出了基于频谱细化与插值法的特征谐波分析方法。首先利用细化选带傅里叶变换(Zoom-FFT)对特征谐波所在局部频段进行细化,然后使用4项5阶Nuttall窗插值法对细化后的频谱进行校正,得到各特征谐波频率、幅值、相位的精确估计。在实验部分,分别使用快速傅里叶变换、Zoom-FFT和提出的Zoom-FFT+4项5阶Nuttall窗插值法对模拟特征谐波信号和24脉波整流装置特征谐波进行了仿真实验。实验结果对比表明,本方法可以有效地抑制栅栏效应和频谱泄漏,各项参数的估计精度明显优于快速傅里叶变换和Zoom-FFT,是一种较为理想的特征谐波分析算法。