Results 61 to 70 of about 5,293 (164)
Detecting LDoS attack based on ASPQ [PDF]
, 2012 Based on the analysis of the effects on average size of packet in the queue which LDoS attack makes,the change of this value was got by simulation on NS2.So detection algorithm was proposed,and was applied on Droptail and RED,which were typical queue ...
Bo LIU +3 more
core
Analysis of the impact of rotor speed variations on the vibration of centrifugal compressor units [PDF]
ObjectiveThe rotor speed of operating centrifugal compressor units needs to be regulated according to working conditions and output requirements. Within the operational speed range, the rotors typically experience fluctuating vibrations in response to ...
Dongzhuo JIA +5 more
core +1 more source
Novel DOA estimation method for coherent wideband LFM signals [PDF]
, 2012 A novel direction of arrival (DOA) estimation method for coherent wideband linear frequency modulation (LFM) signals was proposed.Based on the dechirping property of LFM signal in fractional Fourier domain,a new array data model was constructed,then the ...
Jie-xiao YU +2 more
core
Zhendong Ceshi yu Zhenduan针对传统一维轴承振动信号特征表达效果较弱、轴承故障数据时频特征提取困难及其诊断精度较低等问题，提出一种基于小波变换与注意力机制网络（wavelet transform and attention mechanism net，简称WTA‑Net）的轻量化轴承故障诊断方法。首先，通过小波变换将滚动轴承的一维振动时序信号转化为二维时频图；其次，针对网络训练时梯度消失的问题，提出改进的轻量化骨干网络R‑ResNet18提取二维时频图特征；然后，在网络不同尺度的特征层嵌入时空注意力机制（convolutional
doaj +1 more source
Gaoya dianqi, 2005 为得到PT二次侧干扰信号峰值、单次干扰个数和单次干扰之间的间隔时间等时域特征及干扰信号的频谱（频域特征）,现场实测了变电站500kV隔离开关动作时,电压互感器二次侧的干扰信号。结果表明,隔离开关动作时PT二次侧单次干扰波形是衰减振荡的,干扰主频段0．1-2MHz;在一次隔离开关开或合过程中,有多个脉冲出现,干扰电压峰值近400V。
刘家芳 +5 more
doaj
Mechanism analysis on anisotropic degradation of sandstone in freeze thaw environment based acoustic emission [PDF]
In the freeze-thaw environments, the fracturing of bedding rock poses a significant threat to the stability of the projects in cold regions, leading to potential engineering accidents.
Bing LIU +4 more
core +1 more source
基于Gammatone滤波器组的齿轮系统侧隙诱发冲击特征提取
Jixie chuandong, 2015 齿侧间隙会引发齿间啮合冲击,影响齿轮传动的平稳性和可靠性。为了对故障冲击成分进行提取,提出了基于Gammatone滤波器组的特征提取方法。该方法借鉴听觉系统复杂语音信号识别过程中耳蜗基底膜的信号处理思想,采用与基底膜冲击响应、幅频特性相似的Gammatone滤波器组模型对齿轮系统故障信号进行时频分析,进而提取冲击特征。研究结果表明:Gammatone滤波器组具有对齿轮系统的非平稳瞬变振动信号进行时频分析的功能,该方法能够有效提取由于齿侧间隙引起的啮合冲击故障特征。
高洪波, 李允公, 于良会, 刘杰
doaj +1 more source
GIS隔离开关触头间击穿电弧长度对VFTO波形的时域和频域特征影响分析
Gaoya dianqiGIS中隔离开关在开合短母线时，触头间瞬态击穿将产生VFTO，对设备绝缘构成严重威胁。触头间击穿距离与电弧阻抗特性关联，影响VFTO的时域和频域分布特征。文中为研究GIS隔离开关触头间击穿电弧长度对VFTO波形特征的影响，在GIS隔离开关开合短母线方式1试验中，利用基于电容分压的超宽频电压测量系统准确测量了隔离开关合闸时直流侧全过程VFTO波形，然后提取了前15次预击穿所激发的VFTO波形进行时域、频域以及时频分布分析。通过分析发现，当触头间击穿电弧长度从100 mm减小到30 mm时 ...
廖钧 +6 more
doaj
Gaoya dianqi, 2010 介绍了基于脉冲电流波形用于GIS局部放电检测的新型抗干扰技术。该抗干扰技术由脉冲电流波形的特征提取以及基于波形特征的聚类分析实现。其中,脉冲电流波形的特征提取由基于时频波形和频域波形的等效时频法,而快速聚类分析则由模糊C均值聚类（FCM）实现。受干扰脉冲源影响的电晕放电仿真试验和基于宽带局部放电检测的GIS母线毛刺试验均验证了该新型抗干扰技术的可行性和实用性。
卞超, 陈少波
doaj
Fault diagnosis of ship motor bearings based on multi-domain information fusion and improved ELM [PDF]
ObjectivesAiming at the problems that the symptom parameters from monitoring signals in a single analysis domain fail to fully characterize the operating state of the monitored object, and the model parameters of the Extreme Learning Machine (ELM ...
Chun GE +3 more
core +1 more source