A new time invariant fuzzy time series forecasting method based on particle swarm optimization

In the analysis of time invariant fuzzy time series, fuzzy logic group relationships tables have been generally preferred for determination of fuzzy logic relationships. The reason of this is that it is not need to perform complex matrix operations when these tables are used. On the other hand, when fuzzy logic group relationships tables are exploited, membership values of fuzzy sets are ignored. Thus, in defiance of fuzzy set theory, fuzzy sets’ elements with the highest membership value are only considered. This situation causes information loss and decrease in the explanation power of the model. To deal with these problems, a novel time invariant fuzzy time series forecasting approach is proposed in this study. In the proposed method, membership values in the fuzzy relationship matrix are computed by using particle swarm optimization technique. The method suggested in this study is the first method proposed in the literature in which particle swarm optimization algorithm is used to determine fuzzy relations. In addition, in order to increase forecasting accuracy and make the proposed approach more systematic, the fuzzy c-means clustering method is used for fuzzification of time series in the proposed method. The proposed method is applied to well-known time series to show the forecasting performance of the method. These time series are also analyzed by using some other forecasting methods available in the literature. Then, the results obtained from the proposed method are compared to those produced by the other methods. It is observed that the proposed method gives the most accurate forecasts.     

Two new characteristic parameters for runoff computation

A method capable of estimating the hydrograph from a prescribed storm for a practical mild slope upstream catchment is proposed. This method makes use of two new characteristic parameters, andS, in conjunction with the kinematic wave equation to compute lateral inflows of the main stream of the catchment. The depth profile of overland flow at any instant within the catchment and hydrograph at any location can be easily found. Lag times for individual lateral inflows are then considered and are linearly combined to obtain the hydrograph at the outlet of the catchment or depth profile of the main stream at any instant. The validity of the excess rainfall-surface runoff linear relationship in this study has also been verified with Tatsunokuchiyama catchment, and it shows good results for this computed runoff.     

基于时序特征的发电机转子故障诊断方法

提出了一种利用时序特征进行发电机转子的故障诊断方法.利用时间序列法中的AR或ARMA模型得到的脉冲传递函数的特点,并根据不同故障类别振动信号的格林函数变化的规律性,提出了利用格林函数的统计量特征作为故障诊断的特征参数进行故障诊断的方法.     

基于时间序列模式表示的异常检测算法*

提出了一种基于时间序列的模式表示提取时间序列异常值的异常检测算法(PREOV).时间序列的模式表示本身就具有压缩数据、保持时间序列基本形态的功能,并且具有一定的除噪能力.在时间序列模式表示的基础上提取异常值,可以大大提高算法的效率和准确性,达到事半功倍的效果.在本算法中,还使用了一定的剪枝策略,使得算法的时间复杂度进一步降低.该算法计算简单、实现方便、无须训练,可以支持时间序列的动态增长.     

幂级数和函数的解法综述

本文总结了求幂级数和函数的四种方法。一种方法是将待求级数分解成己知和函数的级数的运算（一般是加减）表达形式,然后逐一求和新的级数;第二种方法是“先求导,再积分”或“先积分,再求导”;第三种方法是把待求级数用基本初等函数的幂级数展开式表示出来;第四种方法是列写出和函数满足的微分方程,解此微分方程得到和函数。     

数控机床热误差的时序分析法建模及其应用

提出了采用时间序列分析法进行机床热误差建模的基本原理及方法,及其在数控机床热误差补偿建模中的应用。利用实测的热误差序列进行时序分析识模、建模和预报。再通过由微机结合机床控制器构成的补偿系统,利用所建立的时序分析模型,经过微机算出补偿值并送入机床控制器对刀架进行附加进给运动完成实时补偿。实验结果表明,可将工件的尺寸变化从原来的25 μm以上降到10 μm以内,大幅度提高了机床的加工精度,从而论证了时序分析法在数控机床热误差建模应用中的可行性与有效性。     

降水和植被变化对龙川江径流量的影响

基于龙川江大峡谷进出口水文控制站楚雄站和小黄瓜园站的长系列水文资料和流域森林盖度变化资料,结合小波分析方法,对降水、植被与径流量变化间相互关系以及径流量各时间尺度准周期变化的本质和形成机制进行了研究。结果表明:研究区降水量序列存在2 a、4 a和14.5 a左右的主周期,径流量序列具有2 a、4 a、6 a和22 a左右的主周期;其中径流量低频振荡所反映的是总径流中来自于壤中水径流和存在于裂隙中的地下水径流的准周期变化,而高频振荡反映的是总径流中来自于地面径流的准周期变化;径流量的年内变化和年际高频振荡主要是由降水量变化所引起的,而径流量序列6 a和22 a的主周期是由土壤和裂隙对降水量序列4 a和14.5 a的主周期滞后放大作用所形成的,径流量序列4 a的主周期是由干热河谷特殊自然地理环境所形成的;径流量与降水量间相互关系在1969年左右发生了突变     

支持向量机及其在径流预测中的应用

给出了支持向量机方法(SVM)的思路、特点及关键之处,探讨了SVM在径流预测中的可能性,并与基于遗传算法的门限回归模型(TR) 进行了对比分析。径流预测实例分析表明,在拟合阶段,SVM模型要好于TR模型;在预留检验阶段,SVM模型与TR模型接近。同时SVM模型适合于小样本情况且能达到全局最优。SVM模型用于径流预测是可行的、优越的。     

简支深梁用和函数法的级数解答

引用和函数法求解弹性力学平面问题, 对简支深梁受三角形荷载作用时的应力进行了分析,同时给出了该问题的付立叶级数解答,该方法不仅将求解弹性力学的偏微分方程组解耦成非耦联的几个偏微分方程,而且其结果与传统的Airy应力函数得到的解答完全一致, 证明了该方法的正确性和适用性,该方法拓展了将经典的弹性力学解析法用于解决工程实际问题的空间。     

含小水电分布式电源的配网线路串联补偿优化

以小水电接入电网为例进行分析研究,深入分析小水电给电网带来的不利影响,重点分析对变压器损耗和线路损耗这两方面的影响。最后,举例某地区小水电接入配电网进行分析研究,对丰水期的小水电加入串联补偿装置后线路电压的变化情况展开研究。