Waveforms play a key role in overlapping time division multiplexing （OvTDM） system. The OvTDM has been proved to be a novel transmission technique that can utilize time diversity to improve the bit error ratio （BER...Waveforms play a key role in overlapping time division multiplexing （OvTDM） system. The OvTDM has been proved to be a novel transmission technique that can utilize time diversity to improve the bit error ratio （BER） performance in Rayleigh channel. According to the resulted law, the BER performance of Gaussian waveform in OvTDM also improves with the increase in the waveform parameter monotonically, and the rectangular waveform is the worst case of Gaussian waveform. In contrast, the spectrum effectiveness of Gaussian waveform OvTDM decreases with the increase in the waveform parameter. In the study, it is obtained that waveforms can achieve the best performance when the smallest correlation coefficient between neighbor symbols is e^-1 .展开更多
目的训练多种机器学习模型用于听性脑干反应(auditory brainstem response,ABR)波形的自动识别,并确定准确率最高的模型,使ABR自动识别技术更好地应用于临床实践。方法选取2021年6月至2022年6月北京清华长庚医院收治的100例听力正常和...目的训练多种机器学习模型用于听性脑干反应(auditory brainstem response,ABR)波形的自动识别,并确定准确率最高的模型,使ABR自动识别技术更好地应用于临床实践。方法选取2021年6月至2022年6月北京清华长庚医院收治的100例听力正常和伴有听力损伤人群的受试者(200耳)为研究对象,根据年龄和听力水平将受试者分为组1(年龄18~59岁,500、1000、2000、4000 Hz频率平均听阈≤25 dB HL)、组2(年龄≥60岁,500、1000、2000、4000 Hz频率平均听阈≤25 dB HL)、组3(年龄18~59岁,500、1000、2000、4000 Hz频率平均听阈>25 dB HL)、组4(年龄≥60岁,500、1000、2000、4000 Hz频率平均听阈>25 dB HL),每组25例。收集受试者纯音测听和ABR数据,提取ABR信号时域和频域特征,与受试者年龄、性别、纯音听阈,刺激声强度以及原始信号序列拼接得到特征向量。分别使用逻辑回归、支持向量机分类、伯努利朴素贝叶斯分类、高斯朴素贝叶斯分类、高斯过程分类、决策树、随机森林、表格网络、轻量化梯度提升框架、极致梯度提升框架和局部级联集成。等机器学习模型对ABR波形进行识别训练,并对整体数据和分组数据分别计算不同模型下波形识别的准确率。结果高斯过程分类模型的整体准确率达到了94.89%,超过了其他机器学习模型。其中95.62%为<60岁听力正常受试者、92.19%为≥60岁听力正常受试者、92.92%为<60岁伴有听力损失受试者、92.50%为≥60岁且伴有听力损失受试者。结论机器学习技术在ABR波形的自动识别方面具有良好的应用前景,高斯过程分类模型优于其他机器学习模型。展开更多
Monitoring seismicity in real time provides significant benefits for timely earthquake warning and analyses.In this study,we propose an automatic workflow based on machine learning(ML)to monitor seismicity in the sout...Monitoring seismicity in real time provides significant benefits for timely earthquake warning and analyses.In this study,we propose an automatic workflow based on machine learning(ML)to monitor seismicity in the southern Sichuan Basin of China.This workflow includes coherent event detection,phase picking,and earthquake location using three-component data from a seismic network.By combining Phase Net,we develop an ML-based earthquake location model called Phase Loc,to conduct real-time monitoring of the local seismicity.The approach allows us to use synthetic samples covering the entire study area to train Phase Loc,addressing the problems of insufficient data samples,imbalanced data distribution,and unreliable labels when training with observed data.We apply the trained model to observed data recorded in the southern Sichuan Basin,China,between September 2018 and March 2019.The results show that the average differences in latitude,longitude,and depth are 5.7 km,6.1 km,and 2 km,respectively,compared to the reference catalog.Phase Loc combines all available phase information to make fast and reliable predictions,even if only a few phases are detected and picked.The proposed workflow may help real-time seismic monitoring in other regions as well.展开更多
传统激光雷达(light detection and ranging,LiDAR)数据处理均采用固定数的波形分解方法,容易遗漏部分重叠的返回波,降低波形拟合精度。为了实现可变数波形分解,本文提出了一种自动确定波形分解数的方法。假定波形数据服从混合高斯分布...传统激光雷达(light detection and ranging,LiDAR)数据处理均采用固定数的波形分解方法,容易遗漏部分重叠的返回波,降低波形拟合精度。为了实现可变数波形分解,本文提出了一种自动确定波形分解数的方法。假定波形数据服从混合高斯分布,并以此建立理想的波形模型;定义用于控制理想模型与实际波形拟合程度的能量函数,用吉布斯分布构建或然率;根据贝叶斯定理构建刻画波形分解的后验概率模型;设计可逆跳转马尔科夫链蒙特卡洛(reversible jump Markov chain Monte Carlo,RJMCMC)算法模拟该后验概率模型,以确定波形分解数并同时完成波形分解。为了验证提出算法的正确性,分别对不同区域的ICESat-GLAS波形数据进行了波形分解试验,定性和定量分析结果验证了本文方法的有效性、可靠性和准确性。展开更多
基金supported by the National Natural Science Foundation of China (90604035)Patent PCT/CN2006/001585.
文摘Waveforms play a key role in overlapping time division multiplexing （OvTDM） system. The OvTDM has been proved to be a novel transmission technique that can utilize time diversity to improve the bit error ratio （BER） performance in Rayleigh channel. According to the resulted law, the BER performance of Gaussian waveform in OvTDM also improves with the increase in the waveform parameter monotonically, and the rectangular waveform is the worst case of Gaussian waveform. In contrast, the spectrum effectiveness of Gaussian waveform OvTDM decreases with the increase in the waveform parameter. In the study, it is obtained that waveforms can achieve the best performance when the smallest correlation coefficient between neighbor symbols is e^-1 .
文摘目的训练多种机器学习模型用于听性脑干反应(auditory brainstem response,ABR)波形的自动识别,并确定准确率最高的模型,使ABR自动识别技术更好地应用于临床实践。方法选取2021年6月至2022年6月北京清华长庚医院收治的100例听力正常和伴有听力损伤人群的受试者(200耳)为研究对象,根据年龄和听力水平将受试者分为组1(年龄18~59岁,500、1000、2000、4000 Hz频率平均听阈≤25 dB HL)、组2(年龄≥60岁,500、1000、2000、4000 Hz频率平均听阈≤25 dB HL)、组3(年龄18~59岁,500、1000、2000、4000 Hz频率平均听阈>25 dB HL)、组4(年龄≥60岁,500、1000、2000、4000 Hz频率平均听阈>25 dB HL),每组25例。收集受试者纯音测听和ABR数据,提取ABR信号时域和频域特征,与受试者年龄、性别、纯音听阈,刺激声强度以及原始信号序列拼接得到特征向量。分别使用逻辑回归、支持向量机分类、伯努利朴素贝叶斯分类、高斯朴素贝叶斯分类、高斯过程分类、决策树、随机森林、表格网络、轻量化梯度提升框架、极致梯度提升框架和局部级联集成。等机器学习模型对ABR波形进行识别训练,并对整体数据和分组数据分别计算不同模型下波形识别的准确率。结果高斯过程分类模型的整体准确率达到了94.89%,超过了其他机器学习模型。其中95.62%为<60岁听力正常受试者、92.19%为≥60岁听力正常受试者、92.92%为<60岁伴有听力损失受试者、92.50%为≥60岁且伴有听力损失受试者。结论机器学习技术在ABR波形的自动识别方面具有良好的应用前景,高斯过程分类模型优于其他机器学习模型。
基金the financial support of the National Key R&D Program of China(2021YFC3000701)the China Seismic Experimental Site in Sichuan-Yunnan(CSES-SY)。
文摘Monitoring seismicity in real time provides significant benefits for timely earthquake warning and analyses.In this study,we propose an automatic workflow based on machine learning(ML)to monitor seismicity in the southern Sichuan Basin of China.This workflow includes coherent event detection,phase picking,and earthquake location using three-component data from a seismic network.By combining Phase Net,we develop an ML-based earthquake location model called Phase Loc,to conduct real-time monitoring of the local seismicity.The approach allows us to use synthetic samples covering the entire study area to train Phase Loc,addressing the problems of insufficient data samples,imbalanced data distribution,and unreliable labels when training with observed data.We apply the trained model to observed data recorded in the southern Sichuan Basin,China,between September 2018 and March 2019.The results show that the average differences in latitude,longitude,and depth are 5.7 km,6.1 km,and 2 km,respectively,compared to the reference catalog.Phase Loc combines all available phase information to make fast and reliable predictions,even if only a few phases are detected and picked.The proposed workflow may help real-time seismic monitoring in other regions as well.
文摘传统激光雷达(light detection and ranging,LiDAR)数据处理均采用固定数的波形分解方法,容易遗漏部分重叠的返回波,降低波形拟合精度。为了实现可变数波形分解,本文提出了一种自动确定波形分解数的方法。假定波形数据服从混合高斯分布,并以此建立理想的波形模型;定义用于控制理想模型与实际波形拟合程度的能量函数,用吉布斯分布构建或然率;根据贝叶斯定理构建刻画波形分解的后验概率模型;设计可逆跳转马尔科夫链蒙特卡洛(reversible jump Markov chain Monte Carlo,RJMCMC)算法模拟该后验概率模型,以确定波形分解数并同时完成波形分解。为了验证提出算法的正确性,分别对不同区域的ICESat-GLAS波形数据进行了波形分解试验,定性和定量分析结果验证了本文方法的有效性、可靠性和准确性。
