Results 11 to 20 of about 1,504,857 (139)
Guangtongxin yanjiu, 2020 噪声传递特性是传送网承载设备的典型时钟同步特性之一。针对传统选频法测试效率较低,且难以全面反映设备带内增益情况的问题,文章通过对时间偏差（TDEV）特性和噪声传递频率响应关系的分析,提出了基于TDEV的时钟噪声传递特性估算方法。实验结果表明,该方法有效解决了现有选频法在测试效率或测试精度方面的不足,可更好地满足现有承载设备时钟和面向5G超高精度的增强型同步以太时钟噪声传递特性的测试需求。
李曙方 +4 more
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Guangtongxin yanjiu, 2013 在UV（紫外光）通信系统中,噪声对信号会产生比较明显的干扰。为了提高系统的通信性能,文章对UV通信系统中的噪声进行了分析。设计了一个模块对噪声进行采样,并分析了PMT（光电倍增管）暗电流噪声、PCB（印制电路板）热噪声、EMI（电磁干扰）噪声以及电源引入的噪声等4种噪声的时域和频域特性,及其对系统性能的影响。为了克服模拟滤波性能不理想的缺点,在接收端采用FPGA（现场可编程门阵列）设计了一个数字滤波器来抑制噪声。实验结果表明,该数字滤波器对SNR（信噪比）有3～7dB的改善。
徐浩然 +5 more
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Guangtongxin yanjiu, 2016 介绍了二阶DRA（分布式拉曼放大器）的结构原理和等效噪声指数,在此基础上,通过实验和理论分析研究了二阶DRA的噪声特性与一阶二阶泵浦注入比例的关系。结果表明,放大器增益基本不变时,二阶泵浦光注入比例越大,等效噪声指数越小;通过适当地调整一阶二阶泵浦功率,可使放大器工作在更小噪声条件下,使整个系统的噪声性能得以提升。
黄金飞, 付成鹏, 余春平
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Study becomes insight: Ecological learning from machine learning
Methods in Ecology and Evolution, Volume 12, Issue 11, Page 2117-2128, November 2021., 2021 Abstract The ecological and environmental science communities have embraced machine learning (ML) for empirical modelling and prediction. However, going beyond prediction to draw insights into underlying functional relationships between response variables and environmental ‘drivers’ is less straightforward.
Qiuyan Yu +5 more
wiley +1 more source
Trends and knowledge gaps in field research investigating effects of anthropogenic noise
Conservation Biology, Volume 35, Issue 1, Page 115-129, February 2021., 2021 Abstract Anthropogenic noise is a globally widespread sensory pollutant, recognized as having potentially adverse effects on function, demography, and physiology in wild animals. Human population growth and associated changes in urbanization, transportation, and resource extraction all contribute to anthropogenic noise and are predicted to increase in ...
Paul Jerem, Fiona Mathews
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Guangtongxin yanjiu, 2016 相位噪声是限制新型调制信号传输性能的主要因素之一。相位噪声监控技术可以实时、动态地获取系统性能,是未来高性能光纤通信系统中的关键技术之一。利用参量放大过程对参与信号相位敏感的特性,提出了一种基于双泵浦参量放大的全光BPSK（二进制相移键控）信号相位噪声监控方案。系统仿真结果表明,针对40Gbit/s BPSK信号,该方案可以实现00.4Vπ范围内相位噪声的全光监控。
董洪光, 余建兴
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Guangtongxin yanjiu, 2014 建立了多跨距RZ-DPSK（归零差分相移键控）色散管理波分复用的简并四波混频噪声标准差的理论计算模型,该模型考虑到了比特序列的随机性和脉冲初始相位的随机性两种随机因素的影响。利用该模型进行了实例分析,研究结果表明:平均功率相同的情况下,DPSK调制信号的噪声标准差值比OOK（开关键控）调制信号的小;比特率的变化对调制信号的噪声标准差值的影响不大;平均功率对调制信号的噪声标准差有很大的影响,随着平均功率的增大,噪声标准差的值呈近似指数形式的增大。
钱立华, 杜建新, 陈秋月
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Effects of spatial autocorrelation and sampling design on estimates of protected area effectiveness
Conservation Biology, Volume 34, Issue 6, Page 1452-1462, December 2020., 2020 Abstract Estimating the effectiveness of protected areas (PAs) in reducing deforestation is useful to support decisions on whether to invest in better management of areas already protected or to create new ones. Statistical matching is commonly used to assess this effectiveness, but spatial autocorrelation and regional differences in protection ...
Pablo Jose Negret +5 more
wiley +1 more source
Decision‐support tools for dynamic management
Conservation Biology, Volume 34, Issue 3, Page 589-599, June 2020., 2020 Abstract Spatial management is a valuable strategy to advance regional goals for nature conservation, economic development, and human health. One challenge of spatial management is navigating the prioritization of multiple features. This challenge becomes more pronounced in dynamic management scenarios, in which boundaries are flexible in space and ...
Heather Welch +4 more
wiley +1 more source
Dizhen xuebao, 2021 选取四川省数字测震台网2015年1月1日至2018年12月31日期间60个固定台站的三分量连续波形记录，计算了台站噪声加速度功率谱密度及相应的概率密度函数分布，统计了不同频率下的噪声功率谱密度值分布，对不同区域、不同频率下背景噪声水平的变化特征予以分析。结果表明：大部分地震台站的高频段噪声由于受到台站附近人为的、规律的作息生活和生产方式的影响，呈现明显的季节性变化和日变化，即夏季噪声水平升高，冬季降低，在农历春节期间达到全年最低值，地理空间分布特征不明显；第二类地脉动冬季噪声水平升高，夏季降低 ...
Jiangtao Xie +3 more
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