Wavelet packet decomposition entropy threshold method for discrete spectrum interferences rejection of on-line partial discharge monitoring

1. Introduction For suppressing discrete spectrum interference (DSI) in partial discharge (PD) signals, the presently wide-used approaches are hardware filters and Fourier transform based digital notch filters [1], which, definitely having gained effect in some extent, lead to relatively large energy loss of original PD signals and the preset parameters wont work when new interference appears or some center frequency changes. Adaptive filters [2] adjust parameters automatically with poor st…     

基于NDVI的2017 年阿根廷大豆分布及长势数据分析

采用遥感手段提取作物分布并监测其长势对动态感知粮食安全具有重要意义。基于MODIS-NDVI产品,结 合阿根廷大豆物候特征,快速提取阿根廷大豆分布及长势情况,并使用农用地连片系数FCI校正由尺度效应造成的面积 失真。在此基础上,使用距平分析监测大豆长势,计算DSI指数监测干旱过程。结果表明：提取的近3年阿根廷大豆种 植面积与美国农业部公布数据变化趋势一致,主产区种植比例高度吻合。2017年阿根廷大豆整体长势较差,副产区长 势优于主产区,各主产省种植空间分布呈现离散或聚集变化。大豆种植面积及分布、长势的变化与干旱过程在时间和 空间上具有高度耦合关系。提出的“物候匹配-LUCC降尺度作物提取法”具有准确快速的特点,通过改良和修正可用 于其他作物的有效提取与监测。     

Simultaneous detection of seven phenolic acids in Danshen injection using HPLC with ultraviolet detector

A high-performance liquid chromatographic (HPLC) method with ultraviolet (UV) detector had been developed for simultaneous quantification of danshensu, protocatechuie aldehyde, caffeic acid, salvianolic acid D, rosmarinic acid, salvianolic acid B and salvianolic acid A in Danshen injection. According to the UV spectra of these components, three detection wavelengths have been selected as follows: 280 nm for danshensu and protocatechuic aldehyde, 326 nm for caffeic acid, salvianolic acid D and rosmarinic acid, 286 nm for salvianolic acid B and salvianolic acid A. The limit of detection (LOD) was improved to be in the range of 0.008～0.160 μg/ml. Moreover, excellent linear behavior over the investigated concentration range was observed, with R>0.999 for all the analytes.