基于缸盖振动信号的发动机排气管堵塞故障分析

现代汽车发动机广泛使用三元催化器进行排放控制,而三元催化器在长期使用过程中容易堵塞,造成发动机排气不畅,影响发动机性能。利用位于发动机缸盖上的振动加速度传感器,提取不同转速下正常状态和堵塞状态的振动信号,通过频谱分析,发现2阶振动幅值有明显变化,经小波包分解求得各频段振动能量,结果表明排气管堵塞后在相同转速下的低频段振动能量都有所减少,而且高转速比低转速减少更加明显,但各频段能量占总能量比重变化不大。此分析结论,可作为发动机排气管堵塞故障诊断的参考依据。     

基于ERP和GPRS的电力生产智能全方位巡检控制系统

针对目前高压输配电线路和设备监管措施较多,对巡线人员工作责任考核技术措施有效性较差的特点,提出了一种新的基于ERP和GPRS的电力生产智能全方位巡检控制系统,阐述了ERP管理模式,引入了ERP和GPRS技术,开发和实现了集巡线工作精确量化管理、巡检数据自动录入等功能于一体的电力生产智能全方位巡检控制系统.应用结果验证了...     

基于支持向量机的张弦梁损伤识别试验

对单榀张弦梁的索力损失和腹杆损伤进行了试验研究.对拉索加载不同程度的预应力来模拟索的预应力损失,利用环境脉动和冲击激励,通过采用Fourier变换或小波变换求得索的频率来计算施加在索上的预应力值.试验结果表明,该方法可以有效地监测索预应力.对张弦梁的上部腹杆进行了环境脉动下的损伤试验,对不同的杆件沿径向进行相应程度的截面切割用以模拟不同程度的损伤状态.对加速度样本进行小波包分解得到特征向量,利用支持向量机对特征向量进行损伤分类,验证了支持向量机方法用于损失识别的有效性.当支持向量机和主成分分析结合后,试验的损伤识别效果有明显的提高.     

数据采集与监控系统在煤层气田地面集输工艺中的应用

根据国内煤层气资源开发情况,借鉴国内外现有成熟的数据采集及监控技术,针对煤层气田低压、低产、井多、井距小等特点和煤层气地面建设成本高、煤层气田数据采集监测系统技术缺乏等问题,介绍一套适合煤层气田特点的数据采集及监控系统。     

面向热泵机组远程监控的GPRS无线数据终端

为了解决热泵多机组的集中管理问题,将基于通用分组无线业务(GPRS)网络的无线通信技术应用于热泵机组的远程监控中;设计了一套面向空气源热泵机组远程数据传输的GPRS无线数据传输终端.该装置采用Cortex_M3内核的高性能单片机STM32F103作为核心测控元件;采用华为GPRS模块EM310作为通信模块,完成基于TC...     

Narrow‐band interference suppression in wavelet packets based multicarrier multicode CDMA overlay system

The wavelet packets based multicarrier (MC) multicode (MCD) code‐division multiple‐access (CDMA) transceiver consists of the MCD part, which ensures the transmission for high speed and flexible data rate; the MC part contributing to robustness to frequency‐selective fading and flexibility for handling multiple data rates; and wavelet packets (WPs) modulation technique, which contributes to the mitigation of the interference problems. As WPs have lower sidelobes compared with sinusoidal carriers, this system is very effective in reducing the problem of inter‐carrier interference. Of course, like any CDMA system, the system can suppress a given amount of interference. This paper considers an interference suppression scheme which will enhance the performance of the system. The receiver employs suppression filters to mitigate the effect of narrow‐band jammer interference. The framework for the system and the performance evaluation are presented in terms of the bit error rate and the outage probability over a Nakagami fading channel. Also, we investigate how the performance is influenced by various parameters, such as the number of taps of the suppression filter and the ratio of narrow‐band interference bandwidth to the spread‐spectrum bandwidth. Finally, the performance of the system is compared with the performance of sinusoidal based MC/MCD‐CDMA system denoted Sin‐MC/MCD‐CDMA. Copyright © 2012 John Wiley & Sons, Ltd.     

Non‐cooperative game‐based packet ferry forwarding for sparse mobile wireless networks

In sparse mobile wireless networks, normally, the mobile nodes are carried by people, and the moving activity of nodes always happens in a specific area, which corresponds to some specific community. Between the isolated communities, there is no stable communication link. Therefore, it is difficult to ensure the effective packet transmission among communities, which leads to the higher packet delivery delay and lower successful delivery ratio. Recently, an additional ferry node was introduced to forward packets between the isolated communities. However, most of the existing algorithms are working on how to control the trajectory of only one ferry work in the network. In this paper, we consider multiple ferries working in the network scenario and put our main focus on the optimal packet selection strategy, under the condition of mutual influence between the ferries and the buffer limitation. We introduce a non‐cooperative Bayesian game to achieve the optimal packet selection strategy. By maximizing the individual income of a ferry, we optimize the network performance on packet delivery delay and successful delivery ratio. Simulation results show that our proposed packet selection strategy improves the network performance on packet delivery delay and successful delivery ratio. Copyright © 2013 John Wiley & Sons, Ltd.     

基于单间隔的暂态选线方法

单相接地故障其暂态特征不受消弧线圈、弧光接地、间歇性接地等影响,但是现有暂态法选线都是基于集中式装置实现的,不利于实现配网保护的就地化实现。本文提出一种仅依赖本间隔零序电流、电压的故障暂态分量进行选线的方法,即暂态小波功率方向选线法,并通过仿真对该方法进行了验证。     

基于小波包分解的逆变器—相开路故障诊断

应用开关函数的双傅里叶变换技术,分析逆变器的直流侧电流的频谱,得出逆变器一相开路故障时的故障特征频率.利用小波包分解的分频特性,对逆变器直流侧电流信号进行小波包分解,求得故障特征频率相应子频带的小波包分解系数的均方根值,并将其作为逆变器一相开路故障的故障特征,以此作为逆变器一相开路故障诊断的依据.试验结果证明了该方法应用于逆变器一相开路故障诊断的可行性.     

适于智能配用电通信的OPS-WDM-PON技术

提出适于智能配用电通信的无源光网络架构.基于异步光分组交换及波分复用技术,构建树形及环形拓扑结构,可提高系统可扩展性及对实时突发业务的随机接入能力.基于空分光交换矩阵和光纤延时线,实现上行信号的冲突解决,可减小分组等待时延,提高冲突解决机制的灵活性.基于自相似流量分布分析了系统波长冲突的丢包率PLR及分组等待时延T.结...