基于特征值能量的压缩采样信号检测方法

压缩采样能够较好地保持稀疏信号的结构和信息,可以在不重构原信号的条件下,直接处理采样数据完成信号检测。本文针对压缩采样信号的盲检测问题,提出一种基于特征值能量的检测算法。该算法对循环频率等于零时的循环自相关矩阵进行分析并实现重构,进而利用分解得到的特征值构造检测统计量,通过研究检测统计量的分布情况确定检测门限,最终实现检测判决。实验结果表明,在相同条件下,该算法具有更好的检测性能和相对低的复杂度。

基于小波包变换的牵引电机转子断条隐患特征提取方法研究

为了实现城轨列车牵引电机在运行时故障隐患的实时监控,根据牵引电机实际运行情况,在Matlab/Simulink仿真环境中建立起了处在闭环控制系统中的带有转子断条隐患的异步电机模型。对定子侧三相电流进行小波包分解并对各频段信号进行小波包系数重构,计算各频段的能量特征值,最后构建出隐患特征向量对电机转子隐患做出诊断。通过对仿真数据的应用,利用上述方法可以有效地识别出电机的转子断条隐患,为研制地铁列车牵引电机隐患挖掘与评估预警系统提供了技术参考。

基于振动信号的变压器故障分析

变压器振动信号可以分析出变压器的运行状态,变压器故障的提前预警可以为电网的安全稳定运行提供保障。基于振动信号的小波包分析,研究了变压器不同运行状态的特点。通过分析可知,变压器发生故障时,振动信号分解后的各频谱信号波高频部分所占的比例比正常时增加了一些,而低频部分所占的比例减少了一些。

Modified multiple-component scattering power decomposition for PolSAR data based on eigenspace of coherency matrix

A modified multiple-component scattering power decomposition for analyzing polarimetric synthetic aperture radar(PolSAR)data is proposed.The modified decomposition involves two distinct steps.Firstly,ei⁃genvectors of the coherency matrix are used to modify the scattering models.Secondly,the entropy and anisotro⁃py of targets are used to improve the volume scattering power.With the guarantee of high double-bounce scatter⁃ing power in the urban areas,the proposed algorithm effectively improves the volume scattering power of vegeta⁃tion areas.The efficacy of the modified multiple-component scattering power decomposition is validated using ac⁃tual AIRSAR PolSAR data.The scattering power obtained through decomposing the original coherency matrix and the coherency matrix after orientation angle compensation is compared with three algorithms.Results from the experiment demonstrate that the proposed decomposition yields more effective scattering power for different PolSAR data sets.

基于小波包与Elman神经网络的整流电路故障诊断

引入了一种针对电励磁双凸极发电机的整流电路故障的小波和Elman神经网络相结合的诊断方法。根据整流电压波形的畸变规律,将2个以内的二极管故障分为7类共计22种故障元。选用Daubechies小波作为小波基,对实测的整流电压进行小波包分析,利用小波系数,在各个频带上进行小波信号重构。提取全频带能量特征值,并以此构造故障模式向量作为神经网络的输入,实现了故障的分类和定位。以一台840W、12/8极的电励磁双凸极发电机为实验样机,通过采集大量故障信号并进行信号处理,以故障特征值的容差范围作为误差判别标准,力求诊断误差最小化。实验结果表明,该方法对被分析信号的频率波动和幅值变化均具有良好的鲁棒性,是一种有效的故障诊断方法,具有较高的故障诊断正确率。

基于小波包分析的双凸极无刷直流发电机系统故障诊断

提出了一种针对电励磁双凸极发电机的整流电路故障诊断方法。根据整流电压波形的畸变规律,将2个以内的二极管故障分为7类共计22种故障元。选用Daubechies小波作为小波基,对实测的整流电压进行小波包分析,利用小波系数,在各个频带上进行小波信号重构。提取全频带能量特征值,并以此构造故障模式向量。以一台840W、12/8极的电励磁双凸极发电机为实验样机,通过采集大量故障信号并进行信号处理,建立整流电路故障档案,为故障识别提供了对照样本。同时,以故障特征值的容差范围作为误差判别标准,力求诊断误差最小化。实验结果表明,该方法对被分析信号的频率波动和幅值变化均具有良好的鲁棒性,是一种有效的特征值提取方法,具有较高的故障诊断正确率。

气液两相流动噪声特性及相含率测量模型

为了研究气液两相流噪声信号特性与体积相含率测量,采用多孔网与多孔孔板相结合的方法,设计了一种适合气液两相流动的噪声发生装置,运用CFD仿真优化设计了新型多孔孔板相含率测量装置,通过在管内设置多孔孔板阻流件,快速调整流场至平衡状态,突出噪声信号,以达到准确测量气液两相相含率的目的。利用声发射技术对流动噪声进行了探测,在河北大学气液两相流测试系统上进行了大量的实验测试,并运用现代信息处理方法对流动声发射信号进行了提取及分析,建立了泡状流、弹状流及过渡流型下气液两相流体积相含率测量模型,测量模型拟合体积含液率相对误差绝对值均低于4.8%。

数字化冲击试验方法的研究

研究数字化冲击试验机的试验原理、力-位移曲线的评定、冲击能量特征值的确定并给出韧性断面率计算公式,为材料表面性能测试提供了一个新的、有效的试验方法。

An approach to estimate tidal dissipation with single-point high-frequency ground wave radar data

Using the single-point ground wave （GW） radar data at Shensi Station and the water level data at three stations （Shengsi, Luchaogang and Daishan）, the authors obtained the flow vectors from the radial velocity of GW radar observation, and calculate four sub-tidal harmonic constants （O1, K1, M2 and S2）. The tidal characteristics derived from the GW radar dataset agreed well with those from the tidal gauge data. The authors also analyzed the tidal energy flux and tidal energy dissipation rate. There was a good relationship between the tidal energy dissipation rate and topography. The study showed a good way to calculate tidal energy dissipation rate using GW radar data.

浅析经验模态分解在电力系统故障中的应用

针对电力系统在当今社会发展的重要性,基于经验模态分解对电力系统故障进行判断,然后利用提取能量特征值的方法,判断出电力系统是否故障。

ADAPTIVE RIVER SEGMENTATION IN SAR IMAGES

There is difficulty for distinguishing of river and shadow in Synthetic Aperture Radar (SAR) images. A method of river segmentation in SAR images based on wavelet energy and gradient is proposed in this paper. It mainly includes two algorithms: coarse segmentation and refined segmen- tation. Firstly, The river regions are coarsely segmented by the wavelet energy feature,and then refined segmented accurately by the gradient threshold which is got adaptively. The experimental results show the validity of the method, which provides a good foundation for targets detection above the river.

Seasonal variation of tidal prism and energy in the Changjiang River estuary： a numerical study

Tidal rivers are intrinsically complex because tidal propagation is influenced by river discharge. This study aims to examine the seasonal variation of tidal prism and energy variance in the tidal river of the Changjiang(Yangtze) River estuary in China. In order to quantify the behaviour of river and tide,we use numerical modelling that has been validated using measured data. We conduct our analysis by quantifying the discharge and energy variance in separate components for both the river and the tide,during wet and dry seasons. We note various definitions of tidal prism and explore the difference between tidal discharge on the flood and ebb and tidal storage volume. The results show that the river discharge attenuates the tidal motion and reduces the tidal flood discharge but the tidal storage volume is approximately constant with different riverine discharge since part of the fresh water discharge is intercepted and captured in the estuary due to the backwater effect. It appears that the tidal discharge adjusts according to the variation of river discharge to keep a constant tidal storage volume. An analysis of the hydraulics shows that the transition from tidal dominance(at the mouth) to river dominance(upstream) depends on the location of tidal current reversal which varies from wet season to dry season. Duringthe wet season,the Changjiang River estuary is totally dominated by energy from fresh water discharge.

基于倍频小波的微生物燃料电池故障诊断

针对微生物燃料电池工作时的常见故障,提出了一种基于倍频小波的故障诊断方法.首先利用倍频小波分析了不同故障情况下的输出电压;然后,利用小波系数重新构建高频信号和低频信号,并提取故障信号的频域特征,从而得出故障信号的主要分布情况;最后诊断出不同类型的故障.所设计的故障诊断方案可以有效提高设备的可靠性和安全性.

Solution of Dirac Equation with Generalized Hylleraas Potential

We employ the parametric generalization of the Nikiforov-Uvarov method to solve the Alhaidari formal- ism of the Dirac equation with a generalized Hylleraas potential of the form V（τ）= V0（a ＋ exp （λτ））/（b ＋ exp （λτ）） ＋ V1（ d ＋ exp （ λτ） ） / （b ＋ exp （λτ））. We obtain the bound state energy eigenvalue and the corresponding eigenfunction ex- pressed in terms of the Jaeobi polynomials. By choosing appropriate parameter in the potential model, the generalized Hylleraas potential reduces to the well known potentials as special cases.