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Integrative Conservation, Volume 3, Issue 4, Page 294-311, December 2024.Freshwater biodiversity in China is threatened by multiple anthropogenic factors, and while there are some reasons to suppose it may be possible to bend the curve of biodiversity loss, the variety of threats and their likely interactions with ongoing climate change provide little basis for optimism. For example, the historic overexploitation of Yangtze
David Dudgeon
wiley +1 more source
Dianci bileiqi, 2016 雷电流可分解为不同的频率分量,目前对于雷电流各频域范围与冲击响应电压之间的对应关系还缺乏相应的研究。在CDEGS中建立土壤电阻率500Ω·m下的100 m长水平接地体模型,利用MATLAB计算研究2.6/50μs雷电流中各频域范围对100 m长水平接地体的冲击电压幅值及幅值时间的影响,研究了将雷电流通过傅里叶变换分解为一系列的离散频率,计算接地极在各频率下的响应电压,再通过傅里叶反变换合成得到雷电流冲击响应电压波形的方法。并通过与CDEGS仿真的雷电流冲击响应电压波形对比分析 ...
马御棠 +6 more
doaj
Dizhen xuebao为了研究地震载荷下圆柱型储罐内液体的晃荡特性，选用15种典型的地震信号，采用计算流体力学软件Fluent进行数值仿真，以探究地震的频率、频率成分、峰值速度以及峰值加速度对晃荡波高和水动压的作用规律。结果表明：① 地震主频是影响自由液面响应的主要因素之一，当其接近储液的一阶固有频率时，会激发强烈的非线性晃荡现象，工程中应添加减晃装置；② 波高与地震峰值速度呈较强的正相关，并且低频成分的地震信号激发的波浪较其它频率成分的地震信号更为剧烈；③ 水动压在储罐上部呈对流模式分布，主要受地震主频和频率成分的影响 ...
Xin Jin +7 more
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Gaoya dianqi, 2023 大型电力变压器绕组的固有振动特性影响其在短路冲击电流下的振动响应及抗短路能力。为了弄清楚固有振动特性与绕组机械参数间的关系，文中建立了计及压板和线圈的绕组轴向振动“质量—弹簧—阻尼”模型，提出了等效质量、刚度和固有振动特性的计算方法。在此基础上，分析了一台SFSZ8-40000/110变压器低压绕组的模态频率和振型，研究了垫块弹性模量、数量和端圈垫块厚度等因素对绕组固有振动特性的影响规律。研究结果表明，绕组各阶轴向振动模态频率之间满足倍数关系，各阶频率对应的振型为绕组不同位置线饼沿轴向的同向和反向振动 ...
刘力卿 +6 more
doaj
Improved pulse shaping for PAPR reduction of OFDM signal [PDF]
, 2012 An improved Nyquist pulse was presented.The proposed pulse waveform can significantly reduce the PAPR and keep the system BER invariant at the same time,but at the expense of a little spectrum loss.Simulation results show that the proposed shaping pulse ...
Bai-yun LUO +3 more
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Social participation challenges and response strategies identified by adults aging with a disability
Journal of Elder Policy, Volume 3, Issue 2, Page 95-109, October 2024.Abstract Social participation is likely to decrease among older adults as disability levels increase. However, it is a modifiable determinant of health that can impact older adults' well‐being and quality of life. Thus, this secondary data analysis aimed to understand what challenges older adults aging with a mobility or vision disability face with ...
Maurita T. Harris, Wendy A. Rogers
wiley +1 more source
Gaoya dianqi, 2012 目前采用频率响应法诊断变压器绕组变形的应用相当广泛,但是在实际测量中,其测试结果会受到诸多因素的影响而失真,若不能准确识别这些影响因素,测试结果的可比性将大大降低,从而给测试结果的分析、判断带来困难甚至错误。笔者结合频率响应法检测技术在天水电网的应用情况,总结了现场由于各种影响因素造成的绕组频率响应曲线异常的实例并将其逐一归类,为今后判断变压器绕组变形提供依据。
曹小龙 +6 more
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
core
Analyzing power errors in the optical pumping system of atomic spin comagnetometers [PDF]
The spin exchange relaxation-free (SERF) atomic comagnetometer is a highly sensitive device designed to measure rotation rates with extreme precision.
Jiale QUAN +4 more
core +1 more source
Integrative Conservation, Volume 3, Issue 3, Page 230-243, September 2024.Tropical secondary forest at early sucessional stage had higher diamter growth rate and mortality rate, however, these forests also are more risked to droughts and high temperatures. Rising temperatures and more frequent droughts may decrease the carbon sink capacity of tropical forest ecosystems. Abstract Tropical forests are major carbon sinks on the
Sai Tun Tun Oo +11 more
wiley +1 more source