Broad-band Frequency Analysis Research Articles

Dominant vibration modes for broadband frequency analysis of multiscale structures with numerous local vibration modes

SummaryIn this paper, an extension of modal analysis in linear computational structural dynamics is presented to deal with complex structures characterized by the presence of numerous local vibration modes and for which the high modal density leads to high‐dimension reduced‐order models. These local modes consist of isolated vibrations that are dissociated from the global vibrations of the structure skeleton and that turn out to often be of negligible contribution to the global dynamics. Therefore, an automatic mode sorting procedure is proposed to extract the dominant modes that represent the global dynamics of the skeleton. Next, an alternative filtering methodology based on a modified eigenvalue problem is presented, which allows to build, a priori, a small‐dimension reduced‐order basis of dominant global modes. The two methods are compared to classic modal analysis using three applications, namely, a heterogeneous plate, a simplified nuclear fuel assembly, and a detailed boiling water reactor fuel assembly.

Study of broadband frequency analysis in stereo-electroencephalography for intractable epilepsy

Objective To investigate the characteristics of preictal and ictal stereo-electroencephalography (SEEG) in intractable epilepsy using multifrequency quantity analysis and to provide neuro-electrophysiological evidence for accurate identification of epileptogenic zone. Methods We retrospectively analyzed the data of 95 intractable epilepsy patients, who underwent preoperative evaluation involving stereo-electroencephalography(SEEG) and subsequent epileptogenic zonectomy between January 2015 and March 2016 at Beijing Tiantan Hospital, Capital Medical University. Preictal and ictal SEEG data of 16 patients, with the sampling rate over 2, 000 Hz, were analyzed using multifrequency quantity method and that patients were followed up for 10.0 ± 2.7 months. Results The ictal onset rhythm in those 16 patients covered the frequency bands of 0.2-4.0 Hz and 8-500 Hz. Notably, the quantitative analysis showed that the infraslow activity (0.2-1.0 Hz), fast activity(12-30 Hz) and high-frequency oscillations (80-500 Hz) were more correlated with the seizure onset zone rather than non-seizure onset zone(P<0.001). Conclusions The infraslow activity (0.2-1.0 Hz) and high-frequency oscillations (80-500 Hz) in the seizure onset zone seem to demonstrate pronounced increase in preictal period. Broadband frequency analysis of ictal electroencephalography (EEG) could facilitate accurate localization of epileptogenic zone by identifying subtle changes that might be difficult to recognize in conventional analysis. Key words: Epilepsy; Electroencephalography; Stereoelectroencephalography; High-frequency oscillations

Measurements of bubbles in sea water by nonstationary sound scattering

Methods for the characterization of bubbles in sea water by acoustic scattering are analyzed. Nonstationary linear and nonlinear sound scattering methods are proposed. The transient linear and nonlinear sound scattering allows the scattering by resonant gas bubbles to be distinguished from the scattering by other microinhomogeneities. The application of parametric arrays in oceanic experiments, together with the broadband frequency analysis of the backscattering coefficient, allows information about bubbles in sea water to be obtained. Experimental results on sound scattering and gas bubble distribution functions are presented for different conditions in the ocean.

Electroencephalographic response to megimide as evaluated by routine EEG interpretation and by broad-band frequency analysis. A study in normal subjects with special reference to the initial nonparoxysmal response.

Acta Neurologica ScandinavicaVolume 41, Issue S13 p. 193-212 ELECTROENCEPHALOGRAPHIC RESPONSE TO MEGIMIDE AS EVALUATED BY ROUTINE EEG INTERPRETATION AND BY BROAD-BAND FREQUENCY ANALYSIS A Study in Normal Subjects with Special Reference to the Initial Nonparoxysmal Response Ulla Selldén, Corresponding Author Ulla Selldén FROM THE LABORATORY OF CLINICAL NEUROPHYSIOLOGY, SAHLGRENSKA SJUKHUSET, GÖTEBORG, SWEDEN.U. Selldén Med. Lic. Klin. Neurofys. Lab. Sahlgrenska Sjukhuset Göteborg SwedenSearch for more papers by this author Ulla Selldén, Corresponding Author Ulla Selldén FROM THE LABORATORY OF CLINICAL NEUROPHYSIOLOGY, SAHLGRENSKA SJUKHUSET, GÖTEBORG, SWEDEN.U. Selldén Med. Lic. Klin. Neurofys. Lab. Sahlgrenska Sjukhuset Göteborg SwedenSearch for more papers by this author First published: April 1965 https://doi.org/10.1111/j.1600-0404.1965.tb01875.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume41, IssueS13April 1965Pages 193-212 RelatedInformation

Effect of sex, psychosocial disadvantages and biological risk factors on EEG maturation

Broad-band frequency analysis was performed on the EEGs of school-age children in order to study the effects of sex, socioeconomic status (SES) and biological risk factors on EEG maturation. Absolute power and relative power in delta, theta, alpha and beta frequency bands were computed in monopolar recordings from F3, F4, C3, C4, P3, P4, O1, O2, F7, F8, T3, T4, T5 and T6. Total absolute power and power in the delta and theta bands decreased with age, following a quadratic polynomial expression. Relative power followed a linear regression with age. Delta and theta decreased while alpha and beta increased. Sex differences in relative power were observed, possibly related to a pubertal spurt: slopes of regression equations were steeper in girls than in boys. Children from low SES (very low income and/or illiterate mother) had higher values of absolute power and a higher percentage of delta and lower of alpha than children with good SES, suggesting a maturational lag. A group of children with personal antecedents of risk factors associated with brain damage were compared with children without antecedents. The former group had higher values of absolute power. Depending on the severity of the risk, children with more severe antecedents had greater differences from children with no antecedents than children in whom antecedents were considered as slight. Risk antecedents had no effect on relative power.

Drug-specific EEG frequency spectra and their time courses produced in the cat by antidepressants and a benzodiazepine

The effects of the tricyclic antidepressants imipramine, desipramine and doxepin and the anti-anxiety agent diazepam were tested for their effects on the frequency distribution of spontaneous brain electrical activity (EEG) in the cat. Multivariate statistical techniques were employed to make an objective and quantitative assessment of the results of broad-band frequency analysis in terms of certain dose-related and drug-specific variables. In spite of several clinical and pharmacological differences in their properties, the antidepressants produced remarkably similar profiles of frequency change which were unrelated to those produced by diazepam.

The quantitative measurement of changes in EEG frequency spectra produced in the cat by sedative-hypnotics and neuroleptics

The sedative-hypnotic secobarbital and the sedative-anti-anxiety agent chlordiazepoxide and two neuroleptics, chlorpromazine and haloperidol, were treated for effects on the EEG of the cat using broad-band frequency analysis of 6 brain sites. Dose-related, ‘drug-specific’ effects were abstracted from the data by the use of multivariate statistical techniques. These demonstrated that the two neuroleptic agents produced very similar alterations in the EEG frequency spectrum which were distinctly different from those resulting from the administration of the sedative-hypnotic and the sedative-anti-anxiety agent. The time-course of the central activity of the 4 compounds was also depicted.

Individual differences in the human electroencephalogram during quiet wakefulness

Biweekly EEGs (O1C3 leads) were recorded under relaxed conditions with the eyes open, from 10 young female subjects throughout the menstrual cycle, and from 2 male subjects. The records were subjected to broad-band frequency analysis of successive 30 sec epochs, during sessions lasting 10 min. Statistical analysis showed that for all amplitude measures, absolute and relative, the variance between different individuals was significantly greater than between repeated measurements in the same individual. The individual differences were expressed in the form of characteristic amplitude profiles for the classical EEG frequency bands. The variance of each subject's profile could be reduced by using a ‘percentage’ amplitude score instead of the absolute values. The individuality of EEG patterns expressed itself also in the ratios between the activities at specific frequencies: a given ratio could be virtually invariant in one or two persons while being highly inconsistent in other subjects. No particular pattern could be discerned in these differences. The present results confirm the existence of a sufficient degree of EEG reproducibility, at least un normal young women, to justify speaking of characteristic individual ‘baseline’ patterns during quiet wakefulness. It will be worthwhile now to investigate if deviations occur from such baselines which might be of importance in psychiatric diagnosis.

An application of long-term frequency analysis in measuring drug-specific alterations in the EEG of the cat

A method is described for the quantitative measurement of “drug-specific” effects on the EEG of the cat. These effects are dose-related and are independent of the normal sources of EEG variation associated with the sleep-waking cycle. Drug-induced changes are expressed as characteristic alterations in frequency spectra and the time courses of these effects are followed for 5 h following administration of the test compounds. Atropine sulfate (0.5 and 2.0 mg/kg) and physostigmine salicylate (0.05 and 0.20 mg/kg) were administered to three unanesthetized and unrestrained cats and a broad-band frequency analysis was performed on the spontaneous brain electrical activity recorded from the prepyriform cortex, ventral hippocampus, lateral geniculate nucleus and the midbrain reticular formation. The resulting data were used as input to discriminant and canonical statistical analysis programs employed to abstract “drug-specific” patterns of frequency change. It was found that both atropine and physostigmine produce alterations in EEG frequency spectra which are clearly distinct from those patterns associated with the sleep-waking cycle and thus neither compound results in what has been characterized as an “EEG-behavioral dissociation”.

Frequency analysis in routine electroencephalography

1. 1. The purpose of this study was to develop an automatic method which could partially substitute for the visual evaluation of EEG background activity. An important indicator was presumed to be the quantity of theta activity (in an awake adult). The great variation of frequency analysis output data does not, however, allow its direct use. 2. 2. It was found that the magnitude of the ratio “theta/alpha”, especially after empirically determined correction, is comparable to the visual estimation of the amount of theta activity. The higher the proposed indicator, the higher the probability that the EEG record will be visually judged as non-normal. The correction is applied by adding the value “30” (if the length of epochs is 15 sec) to the quantity of alpha activity expressed in μVsec. 3. 3. The proposed method could be employed in routine electroencephalography as a supplement to the usual evaluation of background activity. In some special cases (the consideration of focal changes, fast screening of a large number of patients, etc.) it could be applied almost independently. For this purpose an analogue instrument was built which automatically indicates the result of measurement. It is hoped that a simple broad-band frequency analysis may in this way become a useful tool for routine EEG examination.

EEG data representation in broad-band frequency analysis

Possibilities of simplifying data from EEG frequency analysis are discussed. A six filter system is specified. The advantages of “analogue to frequency” inversion and pulsed read out are stressed. A three component frequency profile display system similar to the colour triangle is demonstrated. The effects of electrode placement, sleep and hyperventilation are shown.