共查询到20条相似文献，搜索用时 31 毫秒
1.
Power Quality （PQ） combined disturbances become common along with ubiquity of voltage flickers and harmonics. This paper presents a novel approach to classify the different patterns of PQ combined disturbances. The classification system consists of two parts, namely the feature extraction and the automatic recognition. In the feature extraction stage, Phase Space Reconstruction （PSR）, a time series analysis tool, is utilized to construct disturbance signal trajectories. For these trajectories, several indices are proposed to form the feature vectors. Support Vector Machines （SVMs） are then implemented to recognize the different patterns and to evaluate the efficiencies. The types of disturbances discussed include a combination of short-term disturbances （voltage sags, swells） and long-term disturbances （flickers, harmonics）, as well as their homologous single ones. The feasibilities of the proposed approach are verified by simulation with thousands of PQ events. Comparison studies based on Wavelet Transform （WT） and Artificial Neural Network （ANN） are also reported to show its advantages. 相似文献
2.
In order to investigate the characteristics of sensorimotor cortex during motor execution(ME), voluntary, stimulated and imaginary finger flexions were performed by ten volunteer subjects. Electroencephalogram(EEG) data were recorded according to the modified 10-20 International EEG System. The patterns were compared by the analysis of the motion-evoked EEG signals focusing on the contralateral(C3) and ipsilateral(C4) channels for hemispheric differences. The EEG energy distributions at alpha(8—13 Hz), beta(14—30 Hz) and gamma(30—50 Hz) bands were computed by wavelet transform(WT) and compared by the analysis of variance(ANOVA). The timefrequency(TF) analysis indicated that there existed a contralateral dominance of alpha post-movement event-related synchronization(ERS) pattern during the voluntary task, and that the energy of alpha band increased in the ipsilateral area during the stimulated(median nerve of wrist) task. Besides, the contralateral alpha and beta event-related desynchronization(ERD) patterns were observed in both stimulated and imaginary tasks. Another significant difference was found in the mean power values of gamma band(p0.01)between the imaginary and other tasks. The results show that significant hemispheric differences such as alpha and beta band EEG energy distributions and TF changing phenomena(ERS/ERD) were found between C3 and C4 areas during all of the three patterns. The largest energy distribution was always at the alpha band for each task. 相似文献
3.
利用LabVIEW软件的功能,采用硬件实验和虚拟实验相结合的形式,将LabVIEW应用于生物医学实验教学中。设计了虚拟脑电实验仪,首先通过微弱信号处理实验箱对脑电信号放大滤波,然后利用虚拟仪器技术实现脑电信号的采集、存储、显示和频域分析。 相似文献
4.
In order to classify the alertness status, 19 channels of electroencephalogram（EEG） signals from 5 subjects were acquired during daytime nap. Ten different types of features（including time domain features, frequency domain features and nonlinear features） were extracted from EEG signals, and an improved self-organizing map（ISOM） neuron network was proposed, which successfully identify three different brain status of the subjects： awareness, drowsiness and sleep. Compared with traditional SOM, the experiment results show that the ISOM generates much better classification accuracy, reaching as high as 89.59%. 相似文献
5.
Jiang ZY 《Journal of Zhejiang University. Science. B》2005,6(4):259-264
To investigate inter- and intra-hemispheric electroencephalography (EEG) coherence at rest and during photic stimulation of patients with Alzheimer‘s disease (AD). Thirty-five patients (12 males, 23 females; 52-64 y) and 33 sex- and age-matched controls (12 males, 21 females; 56-65 y) were recruited in the present study. EEG signals from C3-C4, P3-P4, TS-T6 and O1-O2 electrode pairs resulted from the inter-hemispheric action, and EEG signals from C3-P3, C4-P4, P3-O1, P4-O2, C3-O1, C4-O2, TS-O1 and T6-O2 electrode pairs resulted from the intra-hemispheric action. The influence of inter- and intra-hemispheric coherence on EEG activity with eyes closed was examined, using fast Fourier transformation from the 16 sampled channels. The frequencies of photic stimulation were fixed at 5, l0 and 15 Hz, respectively. The general decrease of AD patients in inter- and intra-hemispheric EEG coherence was more significant than that of the normal controls at the resting EEG, with most striking decrease observed in the alpha-1 (8.0-9.0 Hz) and alpha-2 (9.5-12.5 Hz) bands. During photic stimulation, inter- and intra-hemispheric EEG coherences of the AD patients having lower values in the alpha (9.5-10.5 Hz) band than those of the control group. It suggests that under stimulated and non-stimulated conditions, AD patients had impaired inter- and intra-hemispheric functional connections, indicating failure of brain activation in alpha-related frequency. 相似文献
6.
针对癫痫脑电(EEG)信号的非平稳性和非线性,提出一种基于集合经验模式分解(EEMD)提特征并利用最小二乘支持向量机(LS-SVM)的脑电信号分类方法。首先利用EEMD将EEG信号分成多个经验模式分量,得到各阶本征模式分量(IMF),然后提取有效特征,最后用LS-SVM对其进行分类,实验结果表明,该方法对癫痫发作间歇期和发作期EEG的提特征后分类识别正确率达到98%。 相似文献
7.
Wang S Hu HT Wen SQ Wang ZJ Zhang BR Ding MP 《Journal of Zhejiang University. Science. B》2008,9(6):496-499
We described a female patient with insulinoma who experienced recurrent episodes of automatism, confusion and convulsion. Furthermore, her electroencephalography (EEG) findings resembled the pattern in complex partial seizures with secondary generalization. The interictal EEG showed spikes and sharp waves, as well as focal slowing over the left temporal lobe, and the ictal EEG revealed generalized spikes and sharp waves associated with diffused slowing. She was initially misdiagnosed as pharmacoresistant epilepsy. After the insulinoma was found and surgically removed, her EEG turned normal and she was seizure-free during the 4-year follow-up. This report highlights the need for careful reassessment of all seizures refractory to medication, even for the patients associated with epileptiform discharges on EEG. 相似文献
8.
提出了一种采用脑电放大器实现BSPM的方案。方案采用两台64导联脑电放大器采集体表电位信号,通过零相位数字滤波器滤除干扰,最后结合导联布置位置和处理后的信号重构出BSPM。实验结果表明,提出的方案能够有效获取到与心脏电活动对应的BSPM。提出的方法在复杂心脏疾病诊断上具有巨大的潜力。 相似文献
9.
基于分形维前臂动作表面肌电信号的分类 总被引：1，自引：0，他引：1
通过分形维对表面肌电信号进行识别分类.在30个健康志愿者做前臂内旋和外旋时,从他们的右前臂肌前群分别采集2类动作表面肌电信号.当原始动作表面肌电信号用小波包变换分解成几个子信号后,采用一种基于模糊自相似性的方法计算原始信号和4个子信号的分形维.结果表明:从频带0～125 Hz的子信号求得的内旋和外旋动作表面肌电信号的分形维有各自的范围;通过该分形维进行Bayes决策时,错误识别率仅2.26%.因此,该分形维适合用来识别内旋和外旋动作表面肌电信号. 相似文献
10.
提出了基于人工神经网络（ＡｒｔｉｆｉｃｉａｌＮｅｕｒａｌＮｅｔｗｏｒｋｓ）对动力结构进行系统辨识的方法，即应用人工神经网络预测结构地震响应．采用ＢＰ算法的前馈网络（简称ＢＰ网络）对剪切模型结构进行系统辨识．首先用实际地震波及相应的模拟地震响应训练本文提出的ＢＰ网络，然后用“已学会”的ＢＰ网络预测其它地震波激励下的结构地震响应．还讨论了网络拓扑结构、输入单元数等对网络学习和预测的影响．通过本文可以发现，合适的人工神经网络结构能准确地辨识结构动力特性和预测结构动力响应 相似文献
11.
Heart rate variability (HRV) analysis is affected by ectopic beats. An efficient method was proposed to deal with the ectopic
beats. The method was based on trend correlation of the heart timing signal. Predictor of R-R interval (RRI) value at ectopic
beat time was constructed by the weight calculation and the slope estimation of preceding normal RRI. The type of ectopic
beat was detected and replaced by the predictor of RRI. The performance of the simulated signal after ectopic correction was
tested by the standard value using power spectrum density (PSD) estimation, whereas the results of clinical data with ectopic
beats were compared with the adjacent ectopic-free data. The result showed the frequency indexes after ectopy corrected had
less error than other methods with the test of simulated signal and clinical data. It indicated our method could improve the
PSD estimation in HRV analysis. The method had advantages of high accuracy and real time properties to recover the sinus node
modulation. 相似文献
12.
学习过程监控是远程教育的关键环节。学习者在不同学习状态下,脑电波、脉搏、血压、皮温等生物信号会有所不同。基于生物信号采集的远程学习过程监控系统,利用生物传感器采集学习者在线学习时的生物信号,一方面将不同学习者呈现出的生物信号特征分类,建立生物信号分类数据库;另一方面,将动态采集的学习者生物信号通过蓝牙等无线传输方式输入学习终端,再通过Internet输入到远程学习管理中心,通过系统分析软件将采集到的生物信号与学习者生物信号分类数据库进行对比,以获得学习者的实时学习状态,为教师干预和学习者学习提供及时、有针对性的支持服务。基于眼动信号监控学习者疲劳状态的实验证明,利用生物信号采集技术对远程学习过程进行监控,有助于管理者掌握学习者的学习状态,并据此提供个性化学习过程和学习资源支持服务。 相似文献
13.
Kim-seng Chia Herlina Abdul Rahim Ruzairi Abdul Rahim 《Journal of Zhejiang University. Science. B》2012,13(2):145-151
Visible and near infrared spectroscopy is a non-destructive, green, and rapid technology that can be utilized to estimate
the components of interest without conditioning it, as compared with classical analytical methods. The objective of this paper
is to compare the performance of artificial neural network (ANN) (a nonlinear model) and principal component regression (PCR)
(a linear model) based on visible and shortwave near infrared (VIS-SWNIR) (400–1000 nm) spectra in the non-destructive soluble
solids content measurement of an apple. First, we used multiplicative scattering correction to pre-process the spectral data.
Second, PCR was applied to estimate the optimal number of input variables. Third, the input variables with an optimal amount
were used as the inputs of both multiple linear regression and ANN models. The initial weights and the number of hidden neurons
were adjusted to optimize the performance of ANN. Findings suggest that the predictive performance of ANN with two hidden
neurons outperforms that of PCR. 相似文献
14.
A two-layer method based on support vector machines （SVMs） has been developed to distinguish epoxide hydrolases （EHs） from other enzymes and to classify its subfamilies using its primary protein sequences. SVM classifiers were built using three different feature vectors extracted from the primary sequence of EHs： the amino acid composition （AAC）, the dipeptide composition （DPC）, and the pseudo-amino acid composition （PAAC）. Validated by 5-fold cross tests, the first layer SVM classifter can differentiate EHs and non-EHs with an accuracy of 94.2% and has a Matthew＇s correlation coefficient （MCC） of 0.84. Using 2-fold cross validation, PAAC-based second layer SVM can further classify EH subfamilies with an overall accuracy of 90.7% and MCC of 0.87 as compared to AAC （80.0%） and DPC （84.9%）. A program called EHPred has also been developed to assist readers to recognize EHs and to classify their subfamilies using primary protein sequences with greater accuracy. 相似文献
15.
Outlier detection by means of robust regression estimators for use in engineering science 总被引：1，自引：0，他引：1
This study compares the ability of different robust regression estimators to detect and classify outliers. Well-known estimators with high breakdown points were compared using simulated data. Mean success rates （MSR） were computed and used as comparison criteria. The results showed that the least median of squares （LMS） and least trimmed squares （LTS） were the most successful methods for data that included leverage points, masking and swamping effects or critical and concentrated outliers. We recommend using LMS and LTS as diagnostic tools to classify outliers, because they remain robust even when applied to models that are heavily contaminated or that have a complicated structure of outliers. 相似文献
16.
依据星座图采用非参数贝叶斯方法对多元相移键控(MPSK)信号进行调制识别.将未知信噪比(SNR)水平的MPSK信号看成复平面内多个未知均值和方差的高斯分布依照一定的比例混合而成,利用非参数贝叶斯推断方法进行密度估计,实现对MPSK信号分类目的.推断过程中,引入Dirichlet过程作为混合比例因子的先验分布,结合正态逆Wishart(NIW)分布作为均值和方差的先验分布,根据接收信号,利用Gibbs采样的MCMC(Monte Carlo Markov chain)随机采样算法,不断调整混合比例因子、均值和方差.通过多次迭代,得到对调制信号的密度估计.仿真表明,在SNR>5 dB,码元数目大于1 600时,2/4/8PSK的识别率超过了95%. 相似文献
17.
INTRODUCTION Support Vector Machine (SVM) is a relativelynew soft computing method based on statisticallearning theory presented by Vapnik (1995). In SVM,original input space is mapped into a high dimen-sional dot product space called feature space in whichthe optimal hyperplane is determined to maximize thegeneralization ability of the classifier. The optimalhyperplane is found by exploiting a branch ofmathematics, called optimization theory, and re-specting the insights provided by … 相似文献
18.
唐炬 《重庆大学学报(英文版)》2003,2(1)
1. Introduction For suppressing discrete spectrum interference (DSI) in partial discharge (PD) signals, the presently wide-used approaches are hardware filters and Fourier transform based digital notch filters [1], which, definitely having gained effect in some extent, lead to relatively large energy loss of original PD signals and the preset parameters wont work when new interference appears or some center frequency changes. Adaptive filters [2] adjust parameters automatically with poor st… 相似文献
19.
Xiao-cao Shen Cai-xiao Gu Yi-qing Qiu Chuan-jun Du Yan-biao Fu Jian-jun Wu 《Journal of Zhejiang University. Science. B》2009,10(1):1-6
Objective: Adrenocortical carcinoma (ACC) is a rare but highly malignant tumor, and its diagnosis is mostly delayed and prognosis is poor. We report estrogen receptor (ER) expression in this tumor and our clinical experiences with 17 ACC cases. Methods: The data of the 17 patients (9 females and 8 males, age range from 16 to 69 years, mean age of 42.6 years) with ACC were reviewed, and symptoms, diagnostic procedures, treatment, and results of follow-up were evaluated. Immunohistochemistry was used to detect ER expression in tumor samples from the 17 patients. Results: At the time of diagnosis, 4 tumors were classified as Stage Ⅰ, 4 as Stage Ⅱ, 3 as Stage Ⅲ, and 6 as Stage Ⅳ. Eight patients demonstrated positive nuclear immunostaining of ER. The prognosis of patients with ER positive was significantly better (P<0.05) than that of patients with ER negative, with 1- and 5-year survival rates at 86% and 60% for ER-positive patients, and 38% and 0% for ER-negative patients, respectively. Conclusion: ER-positivity may be one of the factors associated with a worse prognosis of ACC. 相似文献
20.
Inter-and intra-hemispheric EEG coherence in patients with mild cognitive impairment at rest and during working memory task 总被引：6，自引：0，他引：6
Objective： To assess functional relationship by calculating inter- and intra-hemispheric electroencephalography （EEG） coherence at rest and during a working memory task of patients with mild cognitive impairment （MCI）. Methods： The sample consisted of 69 subjects： 35 patients （n = 17 males, n = 18 females; 52-71 years old） and 34 normal controls （n = 17 males, n = 17 females; 51 -63 years old）. Mini-mental state examination （MMSE） of two groups revealed that the scores of MCI patients did not differ significantly from those of normal controls （P〉0.05）. In EEG recording, subjects were performed at rest and during working memory task. EEG signals from F3-F4, C3-C4, P3-P4, T5-T6 and O1-O2 electrode pairs are resulted from the inter-hemispheric action, and EEG signals from F3-C3, F4-C4, C3-P3, C4-P4, P3-O1, P4-O2, T5-C3, T6-C4, T5-P3 and T6-P4 electrode pairs are resulted from the intra-hemispheric action for delta （1.0-3.5 Hz）, theta （4.0-7.5 Hz）, alpha-1 （8.0-10.0 Hz）, alpha-2 （10.5-13.0 Hz）, beta-1 （13.5-18.0 Hz） and beta-2 （18.5-30.0 Hz） frequency bands. The influence of inter- and intra-hemispheric coherence on EEG activity with eyes closed was examined using fast Fourier transformation from the 16 sampled channels. Results： During working memory tasks, the inter- and intra-hemispheric EEG coherences in all bands were significantly higher in the MCI group in comparison with those in the control group （P〈0.05）. However, there was no significant difference in inter- and intra-hemispheric EEG coherences between two groups at rest. Conclusion： Experimental results comprise evidence that MCI patients have higher degree of functional connectivity between hemispheres and in hemispheres during working condition, It suggests that MCI may be associated with compensatory processes during working memory tasks between hemispheres and in hemispheres. Moreover, failure of normal cortical connections may exist in MCI patients. 相似文献