Influence of Sinusoidally Modulated Visual Stimuli at Extremely Low Frequency Range on the Human EEG Activity

Volcanoes are increasingly better monitored around the world. Nonetheless, the detection and monitoring of volcanic ash plumes remains difficult, especially in remote areas. Intense electrical activity and lightning in volcanic plumes suggests that electrical monitoring of active volcanoes can aid the detection of ash emissions in near real-time. Current very low frequency and wide-band thunderstorm networks have proven to be able to detect plumes of large magnitude. However, the time delay and the relatively high number of non-detected explosive episodes show that the applicability of these systems to the detection of smaller (and often more frequent) ash-rich explosive events is limited. Here we use a different type of thunderstorm detector to observe electrical discharges generated by the persistent Vulcanian activity of Minamidake crater at Sakurajima volcano in Japan. The sensors consist of two antennas that measure the induced current due to the change in electric field with time. In contrast to the current thunderstorm networks, these sensors measure within the extremely low frequency range (1-45 Hz) and can detect lightning up to 35 kilometres distance.Two detectors were installed at a distance of 3 and 4 kilometres from Minamidake crater and recorded almost continuously since July 2018. Within this period, the ash plumes reached a maximum height of 5.5 kilometres above the crater rim. Using a volcanic lightning detection algorithm and the catalogue of volcanic explosions compiled by the Japan Meteorological Agency (JMA), the number of electrical discharges was determined for each individual explosive event. In addition, the start of electrical discharges was compared to the eruption onset estimated by the JMA.Preliminary results show that the detector closest to the crater had the highest detection efficiency. It detected electrical discharges during 60% of the eruptions listed by the JMA. This is significantly higher than for the World Wide Lightning Location Network, which detected electrical discharges (in the very low frequency range) within 20 kilometres of Sakurajima for less than 0.005% of the eruptions. Furthermore, the results show that for 40% of the detected eruptions, electrical discharges were detected before the estimated JMA timing. Hence, electrical discharges can mark the inception of the explosion with a higher precision and are an indication of ash emission. This demonstrates the value of the cost-effective sensors used here as a monitoring tool at active volcanoes.

Download Full-text

A new ULF-modulated electrostatic wave detected in the extremely low frequency range onboard Geos

Journal of Geophysical Research Atmospheres ◽

10.1029/ja086ia03p01365 ◽

1981 ◽

Vol 86 (A3) ◽

pp. 1365 ◽

Cited By ~ 21

Author(s):

Nicole Cornilleau-Wehrlin

Keyword(s):

Low Frequency ◽

Frequency Range ◽

Electrostatic Wave ◽

Extremely Low Frequency

Download Full-text

The Accuracy of Radio Direction Finding in the Extremely Low Frequency Range

Radio Science ◽

10.1002/2017rs006370 ◽

2017 ◽

Vol 52 (10) ◽

pp. 1245-1252 ◽

Cited By ~ 8

Author(s):

Janusz Mlynarczyk ◽

Andrzej Kulak ◽

Jacobo Salvador

Keyword(s):

Low Frequency ◽

Direction Finding ◽

Frequency Range ◽

Extremely Low Frequency

Download Full-text

A NOTE ON THE CLASSIFICATION OF GEOMAGNETIC SIGNALS BELOW 30 CYCLES PER SECOND

Canadian Journal of Physics ◽

10.1139/p62-105 ◽

1962 ◽

Vol 40 (8) ◽

pp. 1000-1009 ◽

Cited By ~ 8

Author(s):

J. E. Lokken ◽

J. A. Shand ◽

C. S. Wright

Keyword(s):

Geomagnetic Latitude ◽

Low Frequency ◽

Frequency Range ◽

Extremely Low Frequency ◽

Simultaneous Measurements

Simultaneous measurements in the frequency range 0.003 to 30 c.p.s. at a number of widely spaced stations have led to the identification of two general micropulsation classes, impulsive and regular, as well as to an adjacent but independent extremely low frequency (e.l.f.) background. The signal bandwidths and the dependence on geomagnetic latitude and longitude serve to distinguish the classes.

Download Full-text

Empirical and theoretical analysis of the extremely low frequency arterial blood pressure power spectrum in unanesthetized rat

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00135.2006 ◽

2006 ◽

Vol 291 (6) ◽

pp. H2816-H2824 ◽

Cited By ~ 8

Author(s):

David R. Brown ◽

Lisa A. Cassis ◽

Dennis L. Silcox ◽

Laura V. Brown ◽

David C. Randall

Keyword(s):

Blood Pressure ◽

Time Series ◽

Power Spectrum ◽

Arterial Blood Pressure ◽

Low Frequency ◽

Absolute Difference ◽

Frequency Range ◽

Low Frequencies ◽

Extremely Low Frequency ◽

Arterial Blood

The slope of the log of power versus the log of frequency in the arterial blood pressure (BP) power spectrum is classically considered constant over the low-frequency range (i.e., “fractal” behavior), and is quantified by β in the relationship “1/ fβ.” In practice, the fractal range cannot extend to indefinitely low frequencies, but factor(s) that terminate this behavior, and determine β, are unclear. We present 1) data in rats ( n = 8) that reveal an extremely low frequency spectral region (0.083–1 cycle/h), where β approaches 0 (i.e., the “shoulder”); and 2) a model that 1) predicts realistic values of β within that range of the spectrum that conforms to fractal dynamics (∼1–60 cycles/h), 2) offers an explanation for the shoulder, and 3) predicts that the “successive difference” in mean BP (mBP) is an important parameter of circulatory function. We recorded BP for up to 16 days. The absolute difference between successive mBP samples at 0.1 Hz (the successive difference, or Δ) was 1.87 ± 0.21 mmHg (means ± SD). We calculated β for three frequency ranges: 1) 0.083–1; 2) 1–6; and 3) 6–60 cycles/h. The β for all three regions differed ( P < 0.01). For the two higher frequency ranges, β indicated a fractal relationship (β6–60/h = 1.27 ± 0.01; β1–6/h = 1.80 ± 0.16). Conversely, the slope of the lowest frequency region (i.e., the shoulder) was nearly flat (β0.083–1 /h = 0.32 ± 0.28). We simulated the BP time series as a random walk about 100 mmHg with ranges above and below of 10, 30, and 50 mmHg and with Δ from 0.5 to 2.5. The spectrum for the conditions mimicking actual BP time series (i.e., range, 85–115 mmHg; Δ, 2.00) resembled the observed spectra, with β in the lowest frequency range = 0.207 and fractal-like behavior in the two higher frequency ranges (β = 1.707 and 2.057). We suggest that the combined actions of mechanisms limiting the excursion of arterial BP produce the shoulder in the spectrum and that Δ contributes to determining β.

Download Full-text

Theoretical and Experimental Study on Phononic Crystal Structures for Low-Frequency Noise Reduction in the Brake

Volume 14: Vibration, Acoustics and Wave Propagation ◽

10.1115/imece2013-62423 ◽

2013 ◽

Author(s):

Li Shen ◽

Jiu Hui Wu

Keyword(s):

Noise Reduction ◽

Phononic Crystal ◽

Low Frequency ◽

Equivalent Model ◽

Frequency Noise ◽

Steel Matrix ◽

Two Dimensional ◽

Low Frequency Noise ◽

Frequency Range ◽

Extremely Low Frequency

Phononic crystal is an artificial periodic structure in which elastic constants distribute periodically. In this paper, a two dimensional Bragg scattering phononic crystal was introduced into low-frequency noise reduction facility in the brake originally. Through the theoretical analysis by using Plane-wave Expansion Method to obtain the band diagram of a phononic crystal with holes periodically arranged in the 45 carbon steel plate and establishing the equivalent model in motion as the brake, we find an approximate bandgap between 0–5400Hz in the low-frequency range while the complete static bandgaps are distributed in the high-frequency range. It is believed that this kind of extremely low-frequency bandgap is due to the combination of the vibration of a single scatter and the interaction among scatters. In order to demonstrate the theory, contrastive experiment was taken. Noise spectrum diagram of the origin plate without holes was obtained in the first experiment. According to the equivalent model, the two dimensional air column/steel matrix phononic crystal structure in which filling rate was 40% was designed to apply in the test apparatus so that the frequency range (2050 to 2300Hz) of strong noise would be involved in this bandgap. Moreover, the noise in the whole frequency range (0–2550Hz) went down. This phenomenon proved that experiment result was coincident with theoretic consequence. The maximum decreasing amplitude of the noise reached as much as 25dB and the average decreasing amplitude was about 13dB from 2050 to 2300 Hz. In a word, this bandgap which is the combination effect of structure periodicity or the Mie scattering has an obvious extremely low-frequency characteristic in noise and vibration control in the brake.

Download Full-text