time-frequency analysis

时频分析
  • 文章类型: Journal Article
    为解决输油泵中的转子不平衡和不对准问题,提出了一种使用残差网络(ResNet)的创新诊断框架。该模型结合了先进的信号处理算法和战略传感器放置,以增强诊断效能。故障模拟试验台捕获了来自泵上八个关键测量点的振动信号。一维和多维信号处理技术生成了用于训练和验证模型的综合数据集。传感器放置优化,关注轴承座的轴向方向,进口法兰的垂直方向,和出口法兰的轴向方向,提高转子故障灵敏度。通过短时傅里叶变换(STFT)处理的时频数据达到了最高的诊断精度,超过98%。这项研究强调了优化信号处理和精确传感器放置在提高诊断输油泵转子故障的准确性方面的重要性。从而提高能源运输系统的运行可靠性和效率。
    To address rotor imbalance and misalignment in oil transfer pumps, an innovative diagnostic framework using Residual Network (ResNet) is proposed. The model incorporates advanced signal processing algorithms and strategic sensor placement to enhance diagnostic efficacy. A fault simulation test rig captured vibration signals from eight key measurement points on the pump. One-dimensional and multi-dimensional signal processing techniques generated comprehensive datasets for training and validating the model. Sensor placement optimization, focusing on the bearing seat\'s axial direction, inlet flange\'s vertical direction, and outlet flange\'s axial direction, increased rotor fault sensitivity. Time-frequency data processed via Short-Time Fourier Transform (STFT) achieved the highest diagnostic accuracy, surpassing 98 %. This study highlights the importance of optimal signal processing and precise sensor placement in improving the accuracy of diagnosing rotor faults in oil transfer pumps, thus enhancing the operational reliability and efficiency of energy transportation systems.
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  • 文章类型: Journal Article
    EEG的时频(T-F)分析是表征神经活动频谱变化的常用技术。本研究探讨了由于挑战而利用常规光谱技术检查循环事件相关皮质活动的局限性,包括高的试验间变异性。介绍循环频率(C-F)分析,我们旨在加强对周期锁定呼吸事件的评估.对于模拟周期锁定运动前活动的合成脑电图,与传统的T-F分析相比,C-F具有更准确的频率和时间定位,即使试验数量显著减少和呼吸节律的变化。在无负荷呼吸和有负荷呼吸(唤起运动前活动)期间使用真实EEG数据的初步验证表明使用C-F方法的潜在益处。特别是在将时间单位标准化为循环活动阶段以及完善基线位置和持续时间方面。提出的方法可以为有节奏的神经活动的研究提供新的见解,补充T-F分析。 .
    Time-Frequency (T-F) analysis of EEG is a common technique to characterise spectral changes in neural activity. This study explores the limitations of utilizing conventional spectral techniques in examining cyclic event-related cortical activities due to challenges, including high inter-trial variability. Introducing the Cycle-Frequency (C-F) analysis, we aim to enhance the evaluation of cycle-locked respiratory events. For synthetic EEG that mimicked cycle-locked pre-motor activity, C-F had more accurate frequency and time localization compared to conventional T-F analysis, even for a significantly reduced number of trials and a variability of breathing rhythm. Preliminary validations using real EEG data during both unloaded breathing and loaded breathing (that evokes pre-motor activity) suggest potential benefits of using the C-F method, particularly in normalizing time units to cyclic activity phases and refining baseline placement and duration. The proposed approach could provide new insights for the study of rhythmic neural activities, complementing T-F analysis. .
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  • 文章类型: Journal Article
    神经生理大脑活动包括节律性(周期性)和心律失常性(非周期性)信号元素,与行为特征和临床症状有关的研究越来越多。当前神经记录的光谱参数化方法依赖于用户相关的参数选择,这对研究结果的可复制性和稳健性提出了挑战。这里,我们介绍了一种原则性的模型选择方法,依靠贝叶斯信息准则,用于神经生理数据的静态和时间分辨光谱参数化。我们通过地面实况和经验脑磁图记录对该方法进行了广泛的测试。数据驱动的模型选择增强了光谱和谱图分解的特异性和敏感性,即使在非平稳的情况下。总的来说,提出的频谱分解与数据驱动的模型选择最大限度地减少了对用户专业知识和主观选择的依赖,实现更强大的功能,可重复,和可解释的研究结果。
    大脑活动由随时间重复的节律模式和结构化程度较低的心律失常元素组成。脑信号分析的最新进展提高了我们区分这两种类型成分的能力,增强我们对大脑信号的理解。然而,当前的方法需要用户手动调整几个参数以获得结果。因此,分析的结果取决于每个用户的决策和专业知识。为了提高研究成果的可复制性,作者提出了一个新的,自动化方法来简化大脑信号内容的分析。他们开发了一种新算法,该算法定义了由数据通知的分析管道的参数。这种新方法的有效性已通过综合数据和现实数据得到证明。新方法免费提供给所有研究人员,开源app,观察神经科学研究的最佳实践。
    Neurophysiological brain activity comprises rhythmic (periodic) and arrhythmic (aperiodic) signal elements, which are increasingly studied in relation to behavioral traits and clinical symptoms. Current methods for spectral parameterization of neural recordings rely on user-dependent parameter selection, which challenges the replicability and robustness of findings. Here, we introduce a principled approach to model selection, relying on Bayesian information criterion, for static and time-resolved spectral parameterization of neurophysiological data. We present extensive tests of the approach with ground-truth and empirical magnetoencephalography recordings. Data-driven model selection enhances both the specificity and sensitivity of spectral and spectrogram decompositions, even in non-stationary contexts. Overall, the proposed spectral decomposition with data-driven model selection minimizes the reliance on user expertise and subjective choices, enabling more robust, reproducible, and interpretable research findings.
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  • 文章类型: Journal Article
    背景:神经退行性疾病(NDD)由于其衰弱的性质和有限的治疗选择而提出了重大挑战。准确及时的诊断对于优化患者护理和治疗策略至关重要。步态分析,利用可穿戴传感器,在评估与NDD相关的运动异常方面显示出了希望。
    目的:研究问题1在多大程度上分析双肢在时频域中的相互作用可以作为准确分类NDD的合适方法?研究问题2彩色编码图像的利用效果如何,结合深度迁移学习模型,对于NDD的分类?
    方法:使用GaitNDD数据库,包括亨廷顿病患者的录音,肌萎缩侧索硬化,帕金森病,和健康的控制。步态信号经过信号准备,小波相干分析,和用于特征增强的主成分分析。深度迁移学习模型(AlexNet,GoogLeNet,SqueezeNet)用于分类。性能指标,包括准确性,灵敏度,特异性,精度,和F1得分,使用5倍交叉验证进行评估。
    结果:模型的分类性能因使用的时间窗口而异。对于5秒的步态信号段,AlexNet的准确率为95.91%,而GoogLeNet和SqueezeNet的准确率分别为96.49%和92.73%,分别。对于10秒段,AlexNet优于其他模型,准确率为99.20%,而GoogLeNet和SqueezeNet的准确率为96.75%和95.00%,分别。统计检验证实了所提取特征的显著性,表明它们对分类的辨别能力。
    结论:与以前的研究相比,提出的方法表现出优异的性能,为NDD的自动诊断提供非侵入性和具有成本效益的方法。通过使用小波相干性分析步行过程中两条腿之间的相互作用,利用深度迁移学习模型,实现了对NDD的准确分类。
    BACKGROUND: Neurodegenerative diseases (NDDs) pose significant challenges due to their debilitating nature and limited therapeutic options. Accurate and timely diagnosis is crucial for optimizing patient care and treatment strategies. Gait analysis, utilizing wearable sensors, has shown promise in assessing motor abnormalities associated with NDDs.
    OBJECTIVE: Research Question 1 To what extent can analyzing the interaction of both limbs in the time-frequency domain serve as a suitable methodology for accurately classifying NDDs? Research Question 2 How effective is the utilization of color-coded images, in conjunction with deep transfer learning models, for the classification of NDDs?
    METHODS: GaitNDD database was used, comprising recordings from patients with Huntington\'s disease, amyotrophic lateral sclerosis, Parkinson\'s disease, and healthy controls. The gait signals underwent signal preparation, wavelet coherence analysis, and principal component analysis for feature enhancement. Deep transfer learning models (AlexNet, GoogLeNet, SqueezeNet) were employed for classification. Performance metrics, including accuracy, sensitivity, specificity, precision, and F1 score, were evaluated using 5-fold cross-validation.
    RESULTS: The classification performance of the models varied depending on the time window used. For 5-second gait signal segments, AlexNet achieved an accuracy of 95.91 %, while GoogLeNet and SqueezeNet achieved accuracies of 96.49 % and 92.73 %, respectively. For 10-second segments, AlexNet outperformed other models with an accuracy of 99.20 %, while GoogLeNet and SqueezeNet achieved accuracies of 96.75 % and 95.00 %, respectively. Statistical tests confirmed the significance of the extracted features, indicating their discriminative power for classification.
    CONCLUSIONS: The proposed method demonstrated superior performance compared to previous studies, offering a non-invasive and cost-effective approach for the automated diagnosis of NDDs. By analyzing the interaction between both legs during walking using wavelet coherence, and utilizing deep transfer learning models, accurate classification of NDDs was achieved.
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  • 文章类型: Journal Article
    背景:抑郁症的特征通常是奖励功能受损,并在强化学习中显示出改变的奖励动机。本研究进一步探讨了任务难度是否会影响有或没有抑郁症状的大学生的强化学习。
    方法:抑郁症状组(20)和无抑郁症状组(26)完成概率奖励学习任务,中等,和高难度,在该任务中,分析了对奖励的反应偏差和奖励的可识别性。此外,在执行简单的赌博任务时,记录并分析了对奖励和损失反馈的电生理反应。
    结果:当任务很容易时,抑郁症症状组比无抑郁症症状组表现出更多的对奖励的反应偏差,然后随着任务难度的增加,对奖励的反应偏差更快地降低。无抑郁症状组仅在高难度条件下才显示出反应偏差的减少。进一步的回归分析表明,反馈相关的负(FRN)和θ振荡可以预测低难度条件下的响应偏差变化,FRN和theta和delta的振荡可以预测中等和高难度条件下的响应偏差变化。
    结论:对损失和奖励的电生理反应没有记录在与强化学习行为相同的任务中。
    结论:有抑郁症状的大学生在强化学习过程中对任务难度更为敏感。FRN,θ和δ的振荡可以预测奖励倾斜行为。
    BACKGROUND: Depression is usually characterized by impairments in reward function, and shows altered motivation to reward in reinforcement learning. This study further explored whether task difficulty affects reinforcement learning in college students with and without depression symptom.
    METHODS: The depression symptom group (20) and the no depression symptom group (26) completed a probabilistic reward learning task with low, medium, and high difficulty levels, in which task the response bias to reward and the discriminability of reward were analyzed. Additionally, electrophysiological responses to reward and loss feedback were recorded and analyzed while they performed a simple gambling task.
    RESULTS: The depression symptom group showed more response bias to reward than the no depression symptom group when the task was easy and then exhibited more quickly decrease in response bias to reward as task difficulty increased. The no depression symptom group showed a decrease in response bias only in the high-difficulty condition. Further regression analyses showed that, the Feedback-related negativity (FRN) and theta oscillation could predict response bias change in the low-difficulty condition, the FRN and oscillations of theta and delta could predict response bias change in the medium and high-difficulty conditions.
    CONCLUSIONS: The electrophysiological responses to loss and reward were not recorded in the same task as the reinforcement learning behaviors.
    CONCLUSIONS: College students with depression symptom are more sensitive to task difficulty during reinforcement learning. The FRN, and oscillations of theta and delta could predict reward leaning behavior.
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  • 文章类型: Journal Article
    人类活动识别(HAR)与环境辅助生活(AAL)一起,是智能家居不可或缺的组成部分,体育,监视,和调查活动。为了识别日常活动,研究人员专注于轻量级,成本效益高,基于传感器的可穿戴技术与传统的基于视觉的技术一样,缺乏老年人的隐私,每个人的基本权利。然而,从一维多传感器数据中提取潜在特征是具有挑战性的。因此,这项研究的重点是通过一维多传感器数据的时频域分析从光谱图像中提取可区分的模式和深层特征。可穿戴传感器数据,特别是加速器和陀螺仪数据,作为不同日常活动的输入信号,并使用时频分析提供潜在信息。这种潜在的时间序列信息通过称为使用“scalograms”的过程映射到光谱图像中,来自连续小波变换。使用CNN等深度学习模型从活动图像中提取深度活动特征,MobileNetV3、ResNet、和GoogleNet,随后使用常规分类器进行分类。为了验证所提出的模型,使用SisFall和PAMAP2基准测试数据集。根据实验结果,使用Morlet作为具有ResNet-101和softmax分类器的母小波,该模型显示了活动识别的最佳性能,SisFall的准确率为98.4%,PAMAP2的准确率为98.1%,并且优于最先进的算法。
    Human Activity Recognition (HAR), alongside Ambient Assisted Living (AAL), are integral components of smart homes, sports, surveillance, and investigation activities. To recognize daily activities, researchers are focusing on lightweight, cost-effective, wearable sensor-based technologies as traditional vision-based technologies lack elderly privacy, a fundamental right of every human. However, it is challenging to extract potential features from 1D multi-sensor data. Thus, this research focuses on extracting distinguishable patterns and deep features from spectral images by time-frequency-domain analysis of 1D multi-sensor data. Wearable sensor data, particularly accelerator and gyroscope data, act as input signals of different daily activities, and provide potential information using time-frequency analysis. This potential time series information is mapped into spectral images through a process called use of \'scalograms\', derived from the continuous wavelet transform. The deep activity features are extracted from the activity image using deep learning models such as CNN, MobileNetV3, ResNet, and GoogleNet and subsequently classified using a conventional classifier. To validate the proposed model, SisFall and PAMAP2 benchmark datasets are used. Based on the experimental results, this proposed model shows the optimal performance for activity recognition obtaining an accuracy of 98.4% for SisFall and 98.1% for PAMAP2, using Morlet as the mother wavelet with ResNet-101 and a softmax classifier, and outperforms state-of-the-art algorithms.
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  • 文章类型: Journal Article
    这项研究采用了事件相关电位(ERP),时频分析,综合探讨男性身高对第三方惩罚(TPP)的影响及其潜在的神经机制。结果发现,当第三方的身高低于接受者的身高时,惩罚率和更多的转账金额明显更大,这表明男性的身高劣势促进了TPP。神经结果发现,高度劣势诱发的N1较小。高度缺点也引起了更大的P300振幅,更多的θ功率,和更多的阿尔法力量。此外,当第三方处于高度劣势时,观察到rTPJ和后顶叶之间的wPLI明显更强,DLPFC和后顶叶之间的wPLI明显更强。这些结果表明,身高劣势在早期处理阶段会引起负面情绪并影响公平考虑;第三方评估违法者的责任,并在以后做出适当的惩罚决定。我们的发现表明,身高劣势引起的愤怒和声誉关注促进了TPP。当前的研究具有重要意义,因为它强调了男性身高的心理重要性,拓宽了对TPP影响因素的视角,验证了个人劣势对亲社会行为的促进作用,丰富了我们对间接互惠理论的理解,并扩展了拿破仑情结进化论的应用。
    The study employed event-related potential (ERP), time-frequency analysis, and functional connectivity to comprehensively explore the influence of male\'s relative height on third-party punishment (TPP) and its underlying neural mechanism. The results found that punishment rate and transfer amount are significantly greater when the height of the third-party is lower than that of the recipient, suggesting that male\'s height disadvantage promotes TPP. Neural results found that the height disadvantage induced a smaller N1. The height disadvantage also evoked greater P300 amplitude, more theta power, and more alpha power. Furthermore, a significantly stronger wPLI between the rTPJ and the posterior parietal and a significantly stronger wPLI between the DLPFC and the posterior parietal were observed when third-party was at the height disadvantage. These results imply that the height disadvantage causes negative emotions and affects the fairness consideration in the early processing stage; the third-party evaluates the blame of violators and makes an appropriate punishment decision later. Our findings indicate that anger and reputation concern caused by height disadvantage promote TPP. The current study holds significance as it underscores the psychological importance of height in males, broadens the perspective on factors influencing TPP, validates the promoting effect of personal disadvantages on prosocial behavior, enriches our understanding of indirect reciprocity theory, and extends the application of the evolution theory of Napoleon complex.
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  • 文章类型: Journal Article
    共同关注是日常交流不可或缺的工具。共同注意力异常可能是精神分裂症谱系障碍社会损害的关键原因。在这项研究中,我们旨在探索社会情境中与分裂型特征相关的注意取向机制。这里,我们采用了带有社会注意线索的波斯纳线索范式。受试者需要通过凝视和头部方向来检测目标的位置。theta频段的功率用于检查精神分裂症频谱中的注意过程。有四个主要发现。首先,在对无效凝视线索的反应中,分裂型特征与注意力取向之间存在显着关联。第二,具有分裂型性状的个体在θ带表现出神经振荡和同步性的显着激活,这与他们的分裂倾向有关。第三,神经振荡和同步性在社会任务中表现出协同作用,特别是在处理凝视线索时。最后,分裂型性状与注意力取向之间的关系是由theta频带中的神经振荡和同步性介导的。这些发现加深了我们对分裂型性状中θ活性对共同注意力的影响的理解,并为未来的干预策略提供了新的见解。
    Joint attention is an indispensable tool for daily communication. Abnormalities in joint attention may be a key reason underlying social impairment in schizophrenia spectrum disorders. In this study, we aimed to explore the attentional orientation mechanism related to schizotypal traits in a social situation. Here, we employed a Posner cueing paradigm with social attentional cues. Subjects needed to detect the location of a target that is cued by gaze and head orientation. The power in the theta frequency band was used to examine the attentional process in the schizophrenia spectrum. There were four main findings. First, a significant association was found between schizotypal traits and attention orientation in response to invalid gaze cues. Second, individuals with schizotypal traits exhibited significant activation of neural oscillations and synchrony in the theta band, which correlated with their schizotypal tendencies. Third, neural oscillations and synchrony demonstrated a synergistic effect during social tasks, particularly when processing gaze cues. Finally, the relationship between schizotypal traits and attention orientation was mediated by neural oscillations and synchrony in the theta frequency band. These findings deepen our understanding of the impact of theta activity in schizotypal traits on joint attention and offer new insights for future intervention strategies.
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  • 文章类型: Journal Article
    当暴露于地震波时,桥梁可能会受到结构振动响应。结构振动特性分析对于评估桥梁的安全性和稳定性至关重要。在本文中,结合标准时频变换的信号时频特征提取方法(NTFT-ESVD),奇异值分解,利用信息熵对地震激励下结构的振动特性进行了分析。首先,实验模拟了地震作用下结构的响应信号。时频分析的结果表明,在频率检测中,最大相对误差仅为1%,振幅和时间参数的最大相对误差分别为5.9%和6%,分别。这些模拟结果证明了NTFT-ESVD方法在提取信号的时频特征方面的可靠性及其对分析结构地震响应的适用性。然后,分析了台湾恒春地震(2006年)期间苏通长江大桥的真实地震波事件。结果表明,地震波只对桥梁产生短期影响,振动响应的最大振幅不大于1厘米,三维方向的最大振动频率不大于0.2Hz,表明恒春地震不会对苏通长江大桥的稳定和安全产生任何严重影响。此外,通过将其与USGS发布的类似震中距离的地震台站(SSE/WHN/QZN)的结果进行比较,验证了通过从结构振动响应信号中提取时频信息来确定地震波到达时间的可靠性。实例研究结果表明,动态GNSS监测技术与时频分析相结合,可用于分析地震波对桥梁的影响,这对管理者评估结构地震损伤有很大的帮助。
    Bridges may undergo structural vibration responses when exposed to seismic waves. An analysis of structural vibration characteristics is essential for evaluating the safety and stability of a bridge. In this paper, a signal time-frequency feature extraction method (NTFT-ESVD) integrating standard time-frequency transformation, singular value decomposition, and information entropy is proposed to analyze the vibration characteristics of structures under seismic excitation. First, the experiment simulates the response signal of the structure when exposed to seismic waves. The results of the time-frequency analysis indicate a maximum relative error of only 1% in frequency detection, and the maximum relative errors in amplitude and time parameters are 5.9% and 6%, respectively. These simulation results demonstrate the reliability of the NTFT-ESVD method in extracting the time-frequency characteristics of the signal and its suitability for analyzing the seismic response of the structure. Then, a real seismic wave event of the Su-Tong Yangtze River Bridge during the Hengchun earthquake in Taiwan (2006) is analyzed. The results show that the seismic waves only have a short-term impact on the bridge, with the maximum amplitude of the vibration response no greater than 1 cm, and the maximum vibration frequency no greater than 0.2 Hz in the three-dimensional direction, indicating that the earthquake in Hengchun will not have any serious impact on the stability and security of the Su-Tong Yangtze River Bridge. Additionally, the reliability of determining the arrival time of seismic waves by extracting the time-frequency information from structural vibration response signals is validated by comparing it with results from seismic stations (SSE/WHN/QZN) at similar epicenter distances published by the USGS. The results of the case study show that the combination of dynamic GNSS monitoring technology and time-frequency analysis can be used to analyze the impact of seismic waves on the bridge, which is of great help to the manager in assessing structural seismic damage.
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    利用事件相关电位(ERP)的高时间分辨率,我们比较了处理不一致颜色和3D深度信息的时间过程。要求参与者判断食物颜色(颜色条件)或3D结构(3D深度条件)是否与他们先前的知识和经验一致或不一致。行为结果表明,在一致的3D深度条件下的反应时间比在一致的颜色条件下的反应时间慢。在不一致的3D深度条件下的反应时间比在不一致的颜色条件下的反应时间慢。ERP结果表明,与相同的颜色刺激相比,不一致的颜色刺激在前中央区引起更大的N270,更大的P300和更小的N400成分。不一致的3D深度刺激在枕骨区域引起较小的N1,与一致的3D深度刺激相比,顶叶-枕骨区域的P300更大,N400更小。时频分析发现,不一致的颜色刺激比一致的颜色刺激在前中央区域引起更大的theta带激活(360-580ms)。与相同的3D深度刺激相比,不一致的3D深度刺激在顶叶区域引起更大的α和β带激活(240-350ms)。我们的结果表明,人脑在不同的时间过程中处理违反一般颜色或深度知识的问题。我们推测,深度感知冲突主要是通过视觉处理解决问题,而颜色感知冲突主要是通过解决语义违反的问题。
    Utilizing the high temporal resolution of event-related potentials (ERPs), we compared the time course of processing incongruent color versus 3D-depth information. Participants were asked to judge whether the food color (color condition) or 3D structure (3D-depth condition) was congruent or incongruent with their previous knowledge and experience. The behavioral results showed that the reaction times in the congruent 3D-depth condition were slower than those in the congruent color condition. The reaction times in the incongruent 3D-depth condition were slower than those in the incongruent color condition. The ERP results showed that incongruent color stimuli induced a larger N270, larger P300, and smaller N400 components in the fronto-central region than the congruent color stimuli. Incongruent 3D-depth stimuli induced a smaller N1 in the occipital region, larger P300 and smaller N400 in the parietal-occipital region than congruent 3D-depth stimuli. The time-frequency analysis found that incongruent color stimuli induced a larger theta band (360-580 ms) activation in the fronto-central region than congruent color stimuli. Incongruent 3D-depth stimuli induced larger alpha and beta bands (240-350 ms) activation in the parietal region than congruent 3D-depth stimuli. Our results suggest that the human brain deals with violating general color or depth knowledge in different time courses. We speculate that the depth perception conflict was dominated by solving the problem with visual processing, whereas the color perception conflict was dominated by solving the problem with semantic violation.
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