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卷积移时特性的一般形式及应用
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作者 孟宪云 王永茂 高作峰 《齐齐哈尔师范学院学报(自然科学版)》 1993年第2期7-9,共3页
本文给出了一维卷积移时特性的一般形式,提出并证明了n维函数及序列卷积移时的特性。若求f_1(x_1+x_1~′,x_2+x_2~′,…,x_n+x_n~′)*f_2(x_1+x_1^(″),x_2+x_2^(″),…,x_n+x_n^(″))…可先求f_1(x_1,x_2,…,x_n)*f_2(x_1,…,x_n)=g(... 本文给出了一维卷积移时特性的一般形式,提出并证明了n维函数及序列卷积移时的特性。若求f_1(x_1+x_1~′,x_2+x_2~′,…,x_n+x_n~′)*f_2(x_1+x_1^(″),x_2+x_2^(″),…,x_n+x_n^(″))…可先求f_1(x_1,x_2,…,x_n)*f_2(x_1,…,x_n)=g(x_1,x_2,…,x_n)…(2)然后(1)式等于g(x_1+x_1~′+x_1^(″),x_2+x_2~′+x_2^(″),…,x_n+x_n~′+x_n^(″))。其中x_i~′,x_i^(″) (i=1,2,…,n)可正可负。 展开更多
关键词 卷积 移时特性 傅里叶变换
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基于kDBA++聚类算法的谐波污染分区策略 被引量:5
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作者 王杨 唐文楚 +4 位作者 赵劲帅 汪清 张华赢 肖先勇 晁苗苗 《工程科学与技术》 EI CSCD 北大核心 2023年第2期84-96,共13页
随着电网中非线性负荷大量接入及电力电子化率的逐步提升,谐波问题日渐严重,开展电力系统谐波污染区域化治理,是一种有效解决思路。谐波污染分区的意义在于,同一分区内的谐波畸变主要由该分区内的谐波源导致,而受其他分区谐波源影响较... 随着电网中非线性负荷大量接入及电力电子化率的逐步提升,谐波问题日渐严重,开展电力系统谐波污染区域化治理,是一种有效解决思路。谐波污染分区的意义在于,同一分区内的谐波畸变主要由该分区内的谐波源导致,而受其他分区谐波源影响较小。为此,提出了一种抗时移聚类算法kDBA++。首先,考虑到电能质量监测数据具有高维度、含噪声等特点,采用分段聚合近似(picesise aggregate approximation,PAA)算法对数据进行压缩降噪预处理,降低后续计算复杂度。其次,采用kmeans++算法作为逻辑框架。考虑到非同步测量下数据间存在时移现象,难以直接利用kmeans++开展聚类,从而引入动态时间弯曲(dynamic time wraping,DTW)距离对算法进行优化。进而,鉴于DTW距离下聚类质心难以获取,因此采用DTW质心平均算法(DTW barycenter averaging,DBA)克服这一局限性,并最终得到所提kDBA++算法。采用IEEE123节点仿真系统及实际工程案例开展算法对比分析,结果显示所提kDBA++算法聚类精度优于现有算法,可准确进行谐波污染分区。此外,利用谐波污染分区转移阻抗矩阵及谐波贡献度对求得分区加以验证,分析结果表明,各谐波源对其所在分区内节点的谐波畸变影响较大,而对非同一分区节点的影响较小,从而论证了所提方法的实用性和有效性。 展开更多
关键词 谐波污染 监测数据特性 谐波污染分区 kDBA++聚类算法
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Displacement Trends of Slow-moving Landslides: Classification and Forecasting 被引量:7
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作者 CASCINI Leonardo CALVELLO Michele GRIMALDI Giuseppe Maria 《Journal of Mountain Science》 SCIE CSCD 2014年第3期592-606,共15页
A framework is proposed to characterize and forecast the displacement trends of slow-moving landslides, defined as the reactivation stage of phenomena in rocks or fine-grained soils, with movements localized along one... A framework is proposed to characterize and forecast the displacement trends of slow-moving landslides, defined as the reactivation stage of phenomena in rocks or fine-grained soils, with movements localized along one or several existing shear surfaces. The framework is developed based on a thorough analysis of the scientific literature and with reference to significant reported case studies for which a consistent dataset of continuous displacement measurements is available. Three distinct trends of movement are defined to characterize the kinematic behavior of the active stages of slow-moving landslides in a velocity-time plot: a linear trend-type I, which is appropriate for stationary phenomena; a convex shaped trend-type II, which is associated with rapid increases in pore water pressure due to rainfall, followed by a slow decrease in the groundwater level with time; and a concave shaped trend-type III, which denotes a non-stationary process related to the presence of new boundary conditions such as those associated with the development of a newly formed local slip surface that connects with the main existing slip surface. Within the proposed framework, a model is developed to forecast future displacements for active stages of trend-type II based on displacement measurements at the beginning of the stage. The proposed model is validated by application to two case studies. 展开更多
关键词 Slow-moving landslides Displacements forecast Trends of movement
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An investigation of the persistence property of wind power time series 被引量:5
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作者 SUN HaiShun LI JiaMing +4 位作者 LI JingHua Wu Tong WEN JinYu XIE HaiLian YUE ChengYan 《Science China(Technological Sciences)》 SCIE EI CAS 2014年第8期1578-1587,共10页
Mining the inherent persistence property of the time series of wind power is crucial for forecasting and controlling wind power.Few common methods exist that can fully depict and quantify the persistence property.Base... Mining the inherent persistence property of the time series of wind power is crucial for forecasting and controlling wind power.Few common methods exist that can fully depict and quantify the persistence property.Based on the definition of the active power output state of a wind farm,this paper describes the statistical persistence property of the duration time and state transition.Based on the results of our analysis of significant amounts of wind power field measurements,it is found that the duration time of wind power conforms to an inverse Gaussian distribution.Additionally,the state transition matrix of wind power is discovered to yield a ridge property,the gradient of which is related to the time scale of interest.A systemaic methodology is proposed accordingly,allowing the statistical characteristics of the wind power series to be represented appropriately. 展开更多
关键词 characteristics analysis persistence property duration time state transition wind power series
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