An evolutionary approach to pattern-based time series segmentation

Time series data, due to their numerical and continuous nature, are difficult to process, analyze, and mine. However, these tasks become easier when the data can be transformed into meaningful symbols. Most recent works on time series only address how to identify a given pattern from a time series and do not consider the problem of identifying a suitable set of time points for segmenting the time series in accordance with a given set of pattern templates (e.g., a set of technical patterns for stock analysis). However, the use of fixed-length segmentation is an oversimplified approach to this problem; hence, a dynamic approach (with high controllability) is preferable so that the time series can be segmented flexibly and effectively according to the needs of the users and the applications. In view of the fact that this segmentation problem is an optimization problem and evolutionary computation is an appropriate tool to solve it, we propose an evolutionary time series segmentation algorithm. This approach allows a sizeable set of pattern templates to be generated for mining or query. In addition, defining similarity between time series (or time series segments) is of fundamental importance in fitness computation. By identifying the perceptually important points directly from the time domain, time series segments and templates of different lengths can be compared and intuitive pattern matching can be carried out in an effective and efficient manner. Encouraging experimental results are reported from tests that segment both artificial time series generated from the combinations of pattern templates and the time series of selected Hong Kong stocks.     

发电机内冷水微碱性循环处理技术的应用

介绍江西丰城电厂3号机组应用发电机内冷水微碱性循环处理技术的经验和技术原理。江西丰城电厂为了减缓发电机铜线棒的腐蚀，改变传统的采用添加铜缓蚀剂、频繁换水作为发电机内冷却水的调节方式，采用发电机内冷水微碱性循环处理技术。内冷却水通过微碱性处理后含有微量的氢氧化钠，有效地减缓了发电机线棒的腐蚀。     

某末制导雷达VXI总线距离拖引干扰模拟器的设计

距离拖引干扰(RGPO)是现代电子战中干扰末制导雷达距离跟踪系统的一种常用方法.在研制某末制导雷达自动测试系统的过程中,为全面测试雷达的抗干扰能力,迫切需要研制出相应的距离拖引干扰模拟器.本文阐述了距离拖引干扰的基本理论,提出了一种基于VXI总线的距离拖引干扰模拟器的设计方案,该方案采用数字信号处理器(DSP)技术、可编程逻辑器件(CPLD)技术、直接数字频率合成(DDS)技术,实现了距离拖引干扰模拟器的小型化,具有实现简单、控制灵活、可靠性高等特点.经实验验证,该模拟器各项功能指标满足测试雷达性能的要求.     

聚丙烯腈纤维在水浴牵伸过程中应力-应变曲线的研究

主要考察了聚丙烯腈纤维在水浴牵伸过程中的应力—应变曲线，以及温度、牵伸速率、水分对应力—应变曲线的影响。结果表明：聚丙烯腈纤维在水温为室温(26℃)、30℃～70℃时属于细颈牵伸，在80℃、90℃时是类橡胶牵伸，当水温低于60℃和牵伸速率太快时纤维易产生毛丝。所以在牵伸过程中，水温不能低于60％，牵伸速率要适中，在本实验条件下，200mm／min、500mm／min比较合适，而且在水中牵伸比在空气中牵伸效果好，可获得较大的牵伸率。     

一种基于振动数据的旋转机械运行状态评价方法的探讨

旋转机械在工作时容易产生振动,一旦振动异常将严重影响到旋转机械的安全运行,因此振动是评价旋转机械运行状态的重要参数.通过反映旋转机械运行状态的振动特性指标,能对当前振动状态进行识别和评估.通常需要多个指标方能从不同的角度比较完整地反映旋转机械的运行状态,但直接从多个指标中直观地评估旋转机械的运行状态比较困难.该文尝试用一种基于振动数据的评价方法对旋转机械的运行状态进行评估,并通过实验室数据来验证这种方法.结果表明,该方法结论具有较高的可靠性,在工程上易于掌握.     

电机传感器对浸入式泵机械故障监测的实验研究

研究电机在作为激励器完成所需机械输出时,对液压泵站中电机所驱动的浸入式泵机械故障的感知能力,实现现场远程无损监测和诊断.利用电机输出端的电流和电压信号计算出激励器传感器特征参数,并给出了基于统计分析概率密度函数的在线自动监测算法.同时采集了振动信号进行对比分析.实验表明,本文所提出的电机传感器方法可以有效检测出驱动系统中的机械故障.     

工况模态分析理论的概念、应用和发展

简述了近十余年来的工况模态分析理论的概念、应用与发展,提出了今后进一步的研究和发展方向.     

A Study of Modification of M2 Cast High Speed Steel

M2 cast high speed steel was inoculated by addition of rare earth(RE)‐Al‐N, network eutectic carbides were eliminated, matrix structures were refined and the segregation of tungsten and molybdenum elements were relieved. In the condition that the hardness did not decrease, impact toughness obviously increased. Quenching at 1180 °C and three‐times tempering at 560 °C, the hardness of M2 cast high speed steel kept 65~66HRC, impact toughness reached 21.3J/cm². Modified M2 cast high speed steel had excellent thermal fatigue resistance and high temperature wear resistance. Roll made in modified M2 cast high speed steel had excellent service effect using in slit rolling mill stand of hot rolling bar mill.     

卫星数据站接入以太网的方法分析

针对电力系统内部作为应急通信手段的卫星数据通信系统,提出了一种将其与现有的广域网相结合,提高系统利用率的一种方法。