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变分模态分解联合改进小波阈值函数的PPG降噪算法 被引量:2
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作者 刘爽娜 黄德启 王梦梦 《现代电子技术》 2023年第9期61-65,共5页
针对PPG信号采集过程中存在大量混合噪声的问题,提出一种变分模态分解(VMD)改进小波阈值降噪的降噪算法。首先通过傅里叶变换得到脉搏波信号频域信息,确定分解个数和主频率;然后利用变分模态分解算法将含噪声的PPG信号分解为一系列固有... 针对PPG信号采集过程中存在大量混合噪声的问题,提出一种变分模态分解(VMD)改进小波阈值降噪的降噪算法。首先通过傅里叶变换得到脉搏波信号频域信息,确定分解个数和主频率;然后利用变分模态分解算法将含噪声的PPG信号分解为一系列固有模态分量,分解过后确定各分量的中心频率,并筛选有效固有模态分量;最后利用改进后的小波阈值函数对残余噪声进行降噪处理,避免了软阈值的恒定偏差,又保证了阈值函数的连续性,降噪后的信号与原始信号相关系数均值为0.934 7,比变分模态分解方法重构信号提升了7.1%。与其他降噪算法相比,信噪比分别提高了5.77 dB、5.38 dB、4.5 dB,均方根误差分别降低了26.1%、16.8%、7.4%。实验结果表明,通过理论计算、数值模拟和应用研究验证了所提方法的有效性和优越性,在滤波效果和信号保真度之间取得了很好的平衡。 展开更多
关键词 降噪算法 小波阈值函数 信号分解 变分模态分解 降噪处理 理论计算 数值模拟
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学习素养视角下的中学地理研学活动项目化学习设计 被引量:1
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作者 刘双娜 洪祎君 《地理教学》 2022年第11期61-64,50,共5页
学习素养视角下的项目化学习突出学生主体地位,具有实践性强、探究性强的特点。研学旅行作为课程教学的重要内容,各地积极探索开展并积累了大量经验,但同时存在实践性不强、探究性不够的问题。因此,本文基于学习素养的内涵和项目化学习... 学习素养视角下的项目化学习突出学生主体地位,具有实践性强、探究性强的特点。研学旅行作为课程教学的重要内容,各地积极探索开展并积累了大量经验,但同时存在实践性不强、探究性不够的问题。因此,本文基于学习素养的内涵和项目化学习的特征,以探访中国气象局为例,阐述了“双新”背景下,高中地理研学活动的设计与实施。结果显示,学习素养视角下的中学地理研学活动项目化学习设计不仅增强了研学活动实践与探究的学习效果,还促进了学科素养及学习素养的发展。 展开更多
关键词 新课程 学习素养 项目化学习 研学活动 中国气象局
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The spatial distribution of forest carbon sinks and sources in China 被引量:30
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作者 liu shuangna ZHOU Tao +1 位作者 WEI LinYan SHU Yang 《Chinese Science Bulletin》 SCIE EI CAS 2012年第14期1699-1707,共9页
Forest ecosystems play an important role in the global carbon cycle.The implementation of the United Nations Framework Convention on Climate Change(UNFCCC) and the Kyoto Protocol has made the study of forest ecosystem... Forest ecosystems play an important role in the global carbon cycle.The implementation of the United Nations Framework Convention on Climate Change(UNFCCC) and the Kyoto Protocol has made the study of forest ecosystem carbon cycling a hot topic of scientific research globally.This paper utilized Chinese national forest inventory data sets(for the periods 1984-1988 and 1999-2003),the vegetation map of China(1:1000000),and the spatially explicit net primary productivity(NPP) data sets derived with the remote sensing-based light use efficiency model(CASA model).We quantitatively estimated the spatial distribution of carbon sinks and sources of forest vegetation(with a resolution of 1 km) using the spatial downscaling technique.During the period 1984 to 2003 the forest vegetation in China represented a carbon sink.The total storage of carbon increased by 0.77 PgC,with a mean of 51.0TgCa 1.The total carbon sink was 0.88PgC and carbon source was 0.11 PgC during the study period.The carbon sink and carbon source of forest vegetation in China showed a clear spatial distribution pattern.Carbon sinks were mainly located in subtropical and temperate regions,with the highest values in Hainan Province,Hengduan mountain ranges,Changbai mountain ranges in Jilin,and south and northwest of the Da Hinggan Mountains;carbon sources were mainly distributed from the northeast to southwestern areas in China,with the highest values mainly concentrated in southern Yunnan Province,central Sichuan Basin,and northern Da Hinggan Mountains.Increase in NPP was strongly correlated with carbon sink strength.The regression model showed that more than 80% of the variation in the modeled carbon sinks in Northeast,Northern,Northwest and Southern China were explained by the variation in NPP increase.There was a strong relationship between carbon sink strength and forest stand age. 展开更多
关键词 空间分布格局 全球碳循环 中国森林 联合国气候变化框架公约 森林生态系统 CASA模型 森林资源清查 净初级生产力
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