Results 31 to 40 of about 598,873 (167)
Dianci bileiqi, 2016 绝缘子发生污秽放电时的声信号中含有大量能够体现绝缘子污秽程度的信息量,利用傅里叶变换（FFT）将声信号分解为时域和频域两部分,研究在不同污秽度下声信号的时频特性,发现声信号的时域的平均值和频域的频谱特性两方面含有4个特征量,这4个特征量充分体现了绝缘子污秽放电的发展特征。分析得出,声信号时域的均值、最大值、标准差及FFT实部幅值这4个特征量与绝缘子污秽度具有很好的关联性,但是4个特征值对污秽预测结果的影响不尽相同。试验结果表明,绝缘子污秽放电声信号的4个特征量可以作为新的污闪预警特征量。
王洪坤, 聂晶
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Integrative Conservation, Volume 4, Issue 1, Page 45-56, March 2025.Understanding the spatial ecology and movement of snow leopards is crucial for their long‐term conservation. Our first GPS telemetry study in Nepal revealed that snow leopards of Nepal have much larger home ranges than previously thought and frequently cross international borders.
Samundra Ambuhang Subba +21 more
wiley +1 more source
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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Ultrasound in Obstetrics &Gynecology, Volume 65, Issue 1, Page 114-121, January 2025.ABSTRACT Objective Adhesions between the uterus, bladder and anterior abdominal wall are associated with clinical sequelae, including chronic pelvic pain and dyspareunia, and can also yield complications during surgery. The transvaginal sonographic (TVS) sliding bladder sign is a minimally invasive diagnostic tool to evaluate the presence of ...
N. Min +9 more
wiley +1 more source
Gaoya dianqi, 2023 高压断路器是电力系统中的关键设备，其可靠运行是维护电网安全的重要保障。在智能电网的建设下，高压断路器的故障诊断研究受到广泛关注。文中研究了高压断路器不同工况下的机械振动信号，并提出一种基于多特征评估与XGBoost的故障诊断模型。从时域、频域以及时频域提取振动信号的多维特征量，采用融合特征重要性的方法并结合XGBoost模型对多维特征评估筛选，剔除冗余特征量，同时采用贝叶斯优化算法对XGBoost模型中的参数进行优化，提高了分类的准确率。结果表明，基于多特征评估与XGBoost的诊断方法准确率较高 ...
苌瑶 +6 more
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Risk, Hazards &Crisis in Public Policy, Volume 15, Issue 2, Page 203-235, June 2024.Abstract Misinformation presents a challenge to democracies, particularly in times of crisis. One way in which misinformation is spread is through voice messages sent via messenger groups, which enable members to share information on a larger scale. Gaining user perspectives on digital misinformation interventions as countermeasure after detection is ...
Katrin Hartwig +2 more
wiley +1 more source
基于时频分布图像纹理特征的局部放电特高频信号的特征参数提取方法
Gaoya dianqi, 2017 针对局部放电特高频（ultra-high frequency,UHF）信号畸变导致模式识别准确率下降的问题,提出了基于时频分布图像纹理特征的特征参数提取方法。首先对局部放电UHF信号进行s变换得到时频分布图像,然后采用灰度共生矩阵（gray-level co-occurrence matrix,CLCM）算法,从时频分布图像中提取出纹理特征参数。采用主成分分析（principal component analysis,PCA）法对由纹理特征参数构成的特征向量进行降维处理 ...
田妍 +5 more
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基于超宽频电压测量的1100 kV GIL绝缘子闪络电压时频特征试验研究
Gaoya dianqi, 2020 特高压GIL设备是特高压输电工程的重要组成单元,故障精确定位是缩短GIL设备绝缘击穿故障抢修时间,提高特高压输电可靠性的关键。为满足特高压GIL故障精确定位需求,研究特高压GIL设备内部绝缘击穿时所产生暂态电压的波形时频特征是基础。文中利用真型1 100 kV GIL设备构建试验平台,通过模拟盆式绝缘子表面缺陷诱发GIL设备内部绝缘闪络。采用超宽频带的电压测量系统准确测量盆式绝缘子闪络过程中电压突变,通过分析击穿过程暂态电压波形的时域和频域特征,揭示特高压GIL设备盆式绝缘子闪络的电磁波激发机理 ...
丁登伟 +5 more
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Challenges in humanitarian response implementation: a large‐scale review of aid worker perspectives
Disasters, Volume 48, Issue 2, April 2024.Aid workers offer important perspectives for understanding better the most pervasive challenges that arise when implementing emergency response programming in humanitarian settings. This large sample study provides a global review of these perspectives, derived from 4,679 applications to the National NGO Program on Humanitarian Leadership, in which aid
Vincenzo Bollettino +6 more
wiley +1 more source
Gaoya dianqi, 2019 文中提出了一种气体绝缘组合电器（gas insulated switchgear,GIS）超声波检测异常信号的时频特征计算与诊断方法。首先运用希尔伯特—黄变换（Hilbert-Huang transform,HHT）得到描述超声波信号包络线的时频特征的Hilbert幅值谱。在此基础上,给出了离散条件下Hilbert边际谱与平稳性指数的计算方法,分别表示信号中各频率成分的总强度和平稳性。然后将Hilbert边际谱与平稳性指数结合起来分析,可以直观读取信号的时频特征,进而推断出异常气室的故障原因 ...
管敏渊 +7 more
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