Results 81 to 90 of about 12,159 (164)
Hydrochemical characteristics and water quality dynamic analysis of shallow groundwater in Huaibei Plain [PDF]
Shallow groundwater is the most important source of agricultural water supply in Huaibei Plain, and its water quality has attracted wide attention.
Chunfang ZHU +7 more
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Quality Evaluation of Nine Varieties of Blueberry Based on Principal Component Analysis [PDF]
To investigate the quality characteristics of different varieties of blueberry, the quality differences on appearance, physicochemical properties, and sugar and acid composition were analyzed.
Gang LIU +9 more
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Hydrochemical characteristics and component sources of water in underground reservoirs in the Daliuta Coal Mine [PDF]
ObjectiveUnderground reservoirs in coal mines are capable of storing and purifying mine water. A deep understanding of the hydrochemical characteristics and formation mechanisms of water in underground reservoirs is identified as an important ...
Binbin JIANG +6 more
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Gaoya dianqi, 2018 根据目前基于100 MS/s超宽带检测实现多局放源识别和干扰抑制依据的局部放电波形特征提取及分类,指出实现此系统的关键技术为脉冲群波形的快速特征提取。其一般通过对脉冲群时、频域波形进行非线性映射,形成特征参数的2D平面或3D空间,再进行无监督聚类分析即可实现局放源间和噪声源的分离。针对目前应用较多的等效时频法,提出了时频自相法和时频熵法,基于指数模型和蒙特卡洛法产生仿真脉冲群,对上述3种时频算子进行了特征参数2D平面和3D空间的可分类性评定。可分类性测度值表明 ...
魏本刚, 姚周飞, 贺林, 李悦
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Gaoya dianqi, 2020 针对气体绝缘金属全封闭开关设备（gas insulated switchgear,GIS）故障频发问题,提出一种基于振动特征估计的GIS设备故障检测与分析方法;首先,提取GIS设备金属外壳振动信号特征并基于通用自回归模型建立系统的状态空间模型;然后,采用粒子滤波算法对GIS设备振动特征进行估计。同时,将特征估计值与实际测量值之间残差的绝对值作为设备故障检测指标,结合自适应阈值方法来检测故障;最后,依据振动特征残差的变化趋势实现机械故障与放电故障的隔离。对多组变电站现场GIS设备不同故障前 ...
赵洪山, 高玉峰
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Research Progress of Non-destructive Testing Technology in Beef Quality [PDF]
Beef is rich in nutrients and is one of the favored meats among consumers. Market price, consumer willingness to buy and satisfaction are affected by the quality of beef, so it is important to test the quality of beef.
Hao LIU +8 more
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Research Progress on Geographical Origin Traceability and Authentication of Citri Reticulatae Pericarpium [PDF]
Citri Reticulatae Pericarpium (CRP) has both culinary and medicinal uses, with high medicinal and economic value. However, CRP fraud such as mislabeling of the geographical origin, passing off, and aging time cheating has occurred frequently, which ...
LIU Wenwen, WEI Wan, CHEN Yan, ZHAO Jie, FU Manqin, WANG Xu
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Gaoya dianqi, 2011 介绍了基于超声检测的气体绝缘组合电器（gas insulated switchgear,GIS）典型绝缘缺陷识别技术。该技术由基于幅值模式（amplitude mode,AM）、飞行模式（flying mode,FM）、基于相位模式（phase mode,PM）的特征参数提取与判别3个主要模块组成。其中,针对AM提取的特征参数有频率成分50 Hz和100 Hz,用于区分缺陷信号与背景噪声,以及周期最大最小有效值比和周期最大最小峰值比用于区分自由金属微粒和其他超声信号 ...
司文荣, 黄华, 傅晨钊, 李彦明
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Shiyou jixie, 2014 针对石油井架损伤位置识别问题，提出了基于ITD与排列熵的损伤位置特征提取方法。利用ITD方法将锤击响应振动信号分解为一系列PR分量，PR分量更能突出损伤位置信息，计算PR分量的样本熵值，形成的特征向量可分性良好。依据相关性系数选择代表损伤状态主要信息的PR分量，计算其排列熵形成有效的特征向量。以支持向量机为特征向量模式识别器，对比了ITD与近似熵方法所提取特征向量，对于相同有限数量的样本，ITD与样本熵特征向量明显高于ITD与信息熵特征向量的识别率，验证了ITD样本熵方法的有效性 ...
邹龙庆 +3 more
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Gaoya dianqi, 2016 换流器结构复杂,其故障信号难以诊断。文中基于奇异值分解（SVD）和支持向量机（SVM）提出了一种换流器故障诊断的新方法,对选取的故障信号矩阵进行SVD分解,所得奇异值的大小反映故障信息量的大小,选取最大奇异值对应的特征矩阵作为样本,用SVM进行训练分类。当换流器发生故障时,对故障信号矩阵进行SVD分解,用训练所得的SVM诊断器进行故障诊断。仿真表明,SVD分解可以有效提取换流器故障特征,通过SVM可以准确诊断换流器各种故障,文中方法快速准确。
刘霄涵 +4 more
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