基于余弦自卷积窗的高精度介质损耗角测量算法

介质损耗角(dielectric loss angle,DLA)是高压电容器件预防性试验的重要组成部分,实现DLA的精准测量对电力系统稳定运行具有重要意义。在非同步采样和非整数周期截断情况下,利用加截断窗插值算法来提高快速傅里叶变换(fast Fourier transform,FFT)检测DLA的精度;在分析余弦窗函数频谱特性的基础上,提出通过卷积运算并以8项余弦窗为母窗构造余弦自卷积窗(cosine self-convolution window,CSCW)函数;再基于双谱线插值算法原理,推导出2阶CSCW函数的双线插值校正公式,并由此提出了高精度DLA测量方法,精度对比实验表明,该算法能高精准地提取信号相位参数。最后,将加CSCW双谱线插值FFT算法应用于电容型器件的DLA测量,验证了算法的有效性和高精度。     

小波变换在火箭遥测数据误码剔除中的应用

利用MATLAB 仿真,对两段具有代表性的火箭飞行遥测数据进行了小波变换.通过分析不同小波基、分解层数和阈值规则下的处理效果,研究利用小波变换剔除火箭遥测数据误码的可行性.结果表明:对于同一表现形式的遥测数据,只要选择合适的小波基和分解层数,利用小波交换可有效剔除数据中所含误码.     

Maintenance planning using continuous-state partially observable Markov decision processes and non-linear action models

The signs of deterioration in worldwide infrastructure and the associated socio-economic and environmental losses call for sustainable resource management and policy-making. To this end, this work presents an enhanced variant of partially observable Markov decision processes (POMDPs) for the life cycle assessment and maintenance planning of infrastructure. POMDPs comprise a method, commonly employed in the field of robotics, for decision-making on the basis of uncertain observations. In the work presented herein, a continuous-state POMDP formulation is presented which is adapted to the problem of decision-making for optimal management of civil structures. The aforementioned problem may comprise non-linear and non-deterministic action and observation models. The continuous-state POMDP is herein coupled with a normalised unscented transform (NUT) in order to deliver a framework able to tackle non-linearities that likely characterise action models. The capabilities of this enhanced framework and its applicability to the maintenance planning problem are presented via two applications. In a first illustrative example, the use of the NUT is demonstrated within the framework of the value iteration algorithm. Next, the proposed continuous-state framework is compared against a discrete-state formulation for implementation on a life cycle assessment problem.     

Image-Moment Based Affine Invariant Watermarking Scheme Utilizing Neural Networks

Watermarking,as a technique for copyright pro-tection,has drawn significant attention from manyresearchers and there has been intensive research inthis areainrecent years.Robustness of watermarkingstill remains one of the key issues for practical appli-cations.Aserious problemconstrainingsome practicalexplorations of watermarking technologyis the insuf-ficient robustness of existing watermarking algorithmsagainst geometric distortionsuch as rotation,scaling,and translation(RST),etc[1].Designi…     

Adaptive Noise Cancellation Method Used for Wheel Speed Signal of Integrate ABS/ASR System

The anti-lock braking system (ABS) and anti-slip regulation system(ASR) are the very i mportantparts of active safety systems used for modern vehi-cles . This two systems make up of commonintegratesystem ABS/ASR[1 ,2]. At present ,the main controlmethodin ABS/ASRis the logic threshold method.When getting the wheel speed signal ,ECUcomputesand applies control after comparing current signalwith the threshold[3 -5].Because of many reasons ,the wheel speed sig-nals sampled in ABS/ASRalw…     

Digital Image Scrambling Technology Based on the Symmetry of Arnold Transform

Digital i mages are extensively used because of itsfeatures of visibility and abundanceininformation ex-pression. Along with the development of the Inter-net ,the security of storage andtransmission of digitali mages are becoming more and morei mportant .As anapproach of i mage encryption, digital i mage scram-blingtechnologyis aresearchemphasis all through.Itcan be used directlyin digital encryption,andcanalsobe used as the preprocessing and post processing toenhance the robustness of digital…     

基于DWT与改进中值滤波的矿井视频监控图像去噪

井下光照不均、煤尘浓度大以及视频图像获取设备电路电压不稳定等各类因素的存在,导致矿井视频监控系统获取的图像存在大量噪声,影响了对矿井各类生产信息的准确判读。为此,将离散小波变换(Discrete wavelet transform,DWT)与改进中值滤波算法相结合,提出了一种矿井视频监控图像高效去噪算法。首先,对获取的矿井视频图像进行自适应噪声检测,根据检测结果,对图像采用改进中值滤波算法处理;然后对滤波后的图像进行3层离散小波变换,鉴于图像的噪声信息绝大部分集中分布于高频分解系数中,故对低频分解系数不作处理;最后对高频分解系数采用一种改进软阈值去噪函数模型进行去噪,将去噪后的高频分解系数与原始低频分解系数进行重构,得到去噪后清晰度较高的图像。采用实地获取的山西潞安某煤矿井下视频图像进行试验,并与小波软阈值去噪、中值滤波等算法进行去噪效果对比分析,此外,对各算法的试验结果分别采用信噪比(Signal noise ratio,SNR)以及算法运行时间进行评价,结果表明:新算法对于矿井视频监控图像的去噪效果优于其余2类算法,且算法运算时间也具有一定的优势。     

冻结立井爆破冻结壁成形控制与井壁减振研究

控制爆破动载荷对冻结管、冻结壁及井壁的扰动和破坏是冻结井筒施工的重要环节。以万福矿井筒掘进工程为依托,采用周边眼普通光面爆破、半圈切缝药包和整圈切缝药包3种形式,运用多重分形理论,提取了3种条件下冻结壁成形图像多重分形谱特征参数;利用频率切片小波实现了3方案下不同频带信号重构;通过小波包算法对井壁爆破振动进行了监测分析,获取了相应信号频带能量分布。结果表明:多重分形谱可用来客观评价切缝药包对冻结壁的护壁作用;井壁振动信号主频较地面爆破振动高,通常在150 Hz左右;随着频率的升高,井壁振动信号振幅和能量都不断降低;在低频段(0~250 Hz),相对于周边眼普通光面爆破,半圈切缝药包能量降低了41.54%,整圈切缝药包能量降低了52.42%,切缝药包在低频段具有显著的"吸能"作用;在中频段(300~500 Hz),由于半圈切缝药包装药能量释放不均衡及井筒结构体非严格对称导致频带能量出现了"选择放大"效应;在高频段(700~900 Hz),能量沿高程"区域集中"现象说明切缝药包的减振效果更多地体现在爆破近区。验证了切缝药包的减振和对冻结壁的护壁作用。     

基于Hilbert频移的EEMD谐波检测方法

针对经验模态分解(EMD)在谐波检测应用中产生模态混叠的问题,结合EMD分解的局限性和谐波检测实际情况进行分析。首先用集合经验模态分解(EEMD)消除EMD遇到间歇信号干扰出现的模态混叠问题,然后根据谐波信号间的密频问题,提出了基于Hilbert频移的EEMD谐波检测方法。该方法先对谐波信号进行EEMD分解,通过相关度判断相近信号是否发生混叠,若发生混叠,利用Hilbert频移方法使信号满足EEMD分解条件,从而将其分解为单频率分量信号。经仿真验证,该方法能够很好地克服谐波检测中的间歇信号干扰和信号间密频问题,保证了谐波信号有效分解和实用性。通过对实际整流信号的分析证明该方法具有很好的检测效果。     

一种基于Hilbert-Huang变换的电力电缆故障测距方法

为了提高电力电缆故障测距的灵敏性和准确性,提出一种基于Hilbert-Huang变换的电力电缆故障测距方法。针对电缆故障时暂态行波信号奇异性不明显问题,HHT能在不需要选择基函数的条件下对信号进行自适应时频分析,应用经验模态分解(EMD)方法对信号进行唯一分解。EMD能在保持信号良好的时域特性和频域特性的同时得到信号的时频和能量分布关系,有利于提取信号的奇异性,进而减小测量误差。通过不同方法对故障进行数值仿真测距,仿真结果表明HHT故障测距方法具有很好的优越性。