Results 51 to 60 of about 15,391 (174)
Gaoya dianqi, 2018 基于高频法检测局部放电技术已经相对成熟,为了现场检测和对变压器运行状况做出准确诊断,文中提出了利用高频法检测分析放电信号传播特性的方法。通过建立仿真模型确定了频带选择范围,并建立试验平台,利用多传感器同时测量和采集实时信号,对比研究了局部放电在变压器内部传播后以及在不同位置放电时高频信号的频谱特性。结果表明,高频局部放电检测法能够对变压器缺陷进行高效检测且高频信号变化规律明显,为实际的波形检测提供了试验依据。
王新, 苏欢欢, 高树国, 张鹏
doaj
Simulation and Analysis of the Dynamic Range of the Lunar Radar and A New Algorithm for Surface Medium Electromagnetic Parameters Inversion [PDF]
, 2016 探地雷达(GPR)通过向地下发射高频率宽带电磁波来探测地下物体、地层界面以及地下介质属性和分布结构，被广泛应用于经济建设和军事各领域。由于雷达信号会受到各种电磁和背景噪声干扰，使得接收到的信号不能直接准确地反映地下介质信息，造成对目标检测和识别的困难。特别当处于非理想环境条件下，非目标介质反射信号干扰复杂，目标的反射波很难被识别。在对路面、隧道以及地下等检测时，遇到的地下介质多是层状分布的。人们不仅希望获得各层的深度和厚度，还希望得到各层介质的介电常数和电导率等参数。因此，本文将地表层介质作为研究的对象，
俞子伟
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Genomic responses to increased temperature and pollinator selection in Brassica rapa L.
New Phytologist, Volume 250, Issue 2, Page 1231-1247, April 2026.Summary Rapid environmental change reshapes both abiotic stress and biotic interactions, yet it remains unclear how these combined forces structure plants' genomic adaptation. In particular, the joint influence of temperature and pollinator identity, two ecological axes undergoing simultaneous global shifts, has rarely been quantified at genomic ...
Yanqian Ding, Florian P. Schiestl
wiley +1 more source
Technology development in nano-sized photocatalyst powder preparation technologies [PDF]
, 2006 Nano-sized semiconductor powders for use as photocatalysts have great potential in environmental and energy engineering applications. The photocatalytic activity of photocatalyst is significantly affected by preparation process since the crystalline ...
Leung, DYC, Leung, MKH, Ni, M
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Impacts of Human Development on Wildlife Use of Corridors in Botswana 人类开发对博茨瓦纳野生动物廊道利用的影响
Integrative Conservation, Volume 5, Issue 1, Page 164-171, March 2026.This study examined the effect of landscape‐scale human impact on wildlife in Botswana. We examined how species use wildlife corridors in two different human‐dominated landscapes. We identified differences in temporal overlap between wildlife and humans across both landscapes, which is fundamental to consider in both current and future conservation ...
Tempe S. F. Adams +3 more
wiley +1 more source
Gaoya dianqi, 2018 高频变压器在提升电能传输效率的同时,也会加速油纸绝缘系统缺陷的劣化进程。为研究油纸绝缘系统在高频电压下的劣化特性,采用柱板模型模拟油纸绝缘的沿面放电缺陷,搭建高频局部放电试验平台,在10、20、30 k Hz电压下采用恒压法进行多组局部放电试验。利用摄像机和罗氏线圈分别记录试验现象和放电信号,分析高频电压下局部放电图谱和产气特性,并与工频局部放电试验的结果进行对比。结果表明:随着频率的提高,油纸绝缘系统的局部放电起始电压显著降低,单位时间内关键气体的产气量明显提高;但在高频电压下 ...
刘思华 +5 more
doaj
Liquidity Proxies Constructed from Trade Arrival Process and Their Pricing Power [PDF]
, 2016 度量流动性的指标有很多，但基于交易到达过程本身来构建的却非常有限。本文运用带指数响应方程的单变量Hawkes过程对交易到达过程进行建模，以模型参数估计值计算出期望强度和流分支比两个指标。其中，期望强度代表交易密度，是本文研究的流动性不足指标；分支比衡量交易发生的聚集程度，是本文研究的流动性风险指标。然后，我们运用Fama-MacBeth两阶段估计法分别研究了这两个指标对股票收益率的解释能力。实证分析结果显示，在将Fama-French五因子作为控制变量的情况下，期望强度对股票收益率有显著正的解释能力 ...
凌桂芳
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Rare Metals, Volume 45, Issue 3, March 2026.ABSTRACT MCrAlX coatings are widely used as bond coats in thermal barrier coating systems to protect turbine blades from high‐temperature oxidation. However, their oxidation resistance is often restricted by uncontrolled microstructures, surface roughness, and aggregation of reactive elements (REs). In this study, high‐repetition‐rate femtosecond laser
Wei Qian +7 more
wiley +1 more source
滴灌频率和施氮量对温室西葫芦土壤水分、硝态氮分布及产量的影响
Shuitu Baochi Xuebao, 2018 2016年和2017年在北方寒旱地区日光温室西葫芦栽培中，灌溉定额为269.87 mm，设置2个滴灌频率（低频W1：7天1次，高频W2：2天1次）和2个氮素水平（适氮N1：375 kg/hm2，高氮N2：565 kg/hm2），研究不同处理对温室西葫芦土壤水分、硝态氮分布及西葫芦产量的影响。结果表明：（1）高频（W2）滴灌提高了0—40 cm土层的土壤水分，减少了水分的深层下渗。（2）高氮（N2）施肥各土层硝态氮含量较高，适氮处理配合高频次滴灌根区0—40 cm硝态氮含量维持在相对适宜水平，40—80 ...
郭鹏飞 +4 more
doaj
Spectral Analysis and Application in Weak and High-frequency Signal of Optical Fiber Sensors [PDF]
, 2014 在光纤传感系统中，微弱传感信号和高频传感信号的精确检测一直是研究的热点。微弱的光纤传感信号易受到检测仪器的本底噪声或者外界环境的干扰，经常淹没在噪声中，此时无法对微小传感变量进行精确判断。现今提高光纤传感器系统检测精度的方法大都为对光纤传感器的结构进行改进或对传感信号进行时域的降噪处理。在结构改进方面可以采用低噪声高放大倍数的光电转换电路或在解调系统中引入干涉仪等，但这些方式都会增加的传感系统的成本及复杂度，特别是干涉仪的引用还会降低系统的抗干扰性。对传感信号进行降噪处理如采用小波变换 ...
陈熙
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