scholarly journals Magnetic Field Mapping and Correction for Moving OP-MEG

2021 ◽  
Author(s):  
Stephanie J Mellor ◽  
Tim M Tierney ◽  
George C O'Neill ◽  
Nicholas Alexander ◽  
Robert A Seymour ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Brain Activity ◽  
Low Frequency ◽  
Optically Pumped ◽  
Magnetic Field Mapping ◽  
Modelling Method ◽  
Movement Artefact ◽  
Power Spectral ◽  
Background Magnetic Field ◽  
The Magnetic Field

Background: Optically pumped magnetometers (OPMs) have made moving, wearable magnetoencephalography (MEG) possible. The OPMs typically used for MEG require a low background magnetic field to operate, which is achieved using both passive and active magnetic shielding. However, the background magnetic field is never truly zero Tesla, and so the field at each of the OPMs changes as the participant moves. This leads to position and orientation dependent changes in the measurements, which manifest as low frequency artefacts in MEG data. Objective: We modelled the spatial variation in the magnetic field and used the model to predict the movement artefact found in a dataset. Methods: We demonstrate a method for modelling this field with a triaxial magnetometer, then showed that we can use the same technique to predict the movement artefact in a real OPM-based MEG (OP-MEG) dataset. Results: Using an 86-channel OP-MEG system, we found that this modelling method maximally reduced the power spectral density of the data by 26.2 ± 0.6 dB at 0 Hz, when applied over 5 s non-overlapping windows. Conclusion: The magnetic field inside our state-of-the art magnetically shielded room can be well described by low-order spherical harmonic functions. We achieved a large reduction in movement noise when we applied this model to OP-MEG data. Significance: Real-time implementation of this method could reduce passive shielding requirements for OP-MEG recording and allow the measurement of low-frequency brain activity during natural participant movement.

Magnetic Field Intensity Gradient Method on the Detection of a Remote Target

2013 ◽  
Vol 706-708 ◽  
pp. 845-848
Author(s):  
Ying Chun Huan ◽  
Chun Sheng Lin
Keyword(s):  
Magnetic Field ◽  
Magnetic Dipole ◽  
Field Intensity ◽  
Gradient Method ◽  
Magnetic Field Intensity ◽  
Intensity Gradient ◽  
Optically Pumped ◽  
Background Magnetic Field ◽  
Magnetic Detection ◽  
The Magnetic Field

Based on the spheroid and magnetic dipole mixed array model, the magnetic field intensity gradient of ship is measured by using buoys and optically pumped magnetometers in order to achieve the purpose of eliminating the interference of the background magnetic field, thereby effectively improving magnetic detection of remote targets.

PEMANFAATAN RADIASI ENERGI TEGANGAN 150 KV UNTUK LAMPU LED PENERANGAN JALAN

Jurnal Teknik ◽  
2018 ◽  
Vol 7 (1) ◽  
Author(s):  
Mauludi Manfaluthy
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
High Voltage ◽  
Low Frequency ◽  
Energy Utilization ◽  
World Health ◽  
Electromagnetic Signals ◽  
Health Organization ◽  
The Magnetic Field ◽  
Low Frequency Waves

WHO (World Health Organization) concludes that not much effect is caused by electric field up to 20 kV / m in humans. WHO standard also mentions that humans will not be affected by the magnetic field under  100 micro tesla and that the electric field will affect the human body with a maximum standard of 5,000 volts per meter. In this study did not discuss about the effect of high voltage radiation SUTT (High Voltage Air Channel) with human health. The research will focus on energy utilization of SUTT radiation. The combination of electric field and magnetic field on SUTT (70-150KV) can generate electromagnetic (EM) and radiation waves, which are expected to be converted to turn on street lights around the location of high voltage areas or into other forms. The design of this prototype works like an antenna in general that captures electromagnetic signals and converts them into AC waves. With a capacitor that can store the potential energy of AC and Schottky diode waves created specifically for low frequency waves, make the current into one direction (DC). From the research results obtained the current generated from the radiation is very small even though the voltage is big enough.Keywords : Radiance Energy, Joule Thief, and  LED Module.

scholarly journals Integral Equations for Problems on Wave Propagation in Near-Earth Plasma

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1395
Author(s):  
Danila Kostarev ◽  
Dmitri Klimushkin ◽  
Pavel Mager
Keyword(s):  
Magnetic Field ◽  
Integral Equations ◽  
Field Potential ◽  
Low Frequency ◽  
Fredholm Equation ◽  
Compression Waves ◽  
Parallel Component ◽  
Electric Field Potential ◽  
The Magnetic Field ◽  
Low Frequency Waves

We consider the solutions of two integrodifferential equations in this work. These equations describe the ultra-low frequency waves in the dipol-like model of the magnetosphere in the gyrokinetic framework. The first one is reduced to the homogeneous, second kind Fredholm equation. This equation describes the structure of the parallel component of the magnetic field of drift-compression waves along the Earth’s magnetic field. The second equation is reduced to the inhomogeneous, second kind Fredholm equation. This equation describes the field-aligned structure of the parallel electric field potential of Alfvén waves. Both integral equations are solved numerically.

On the existence of compressional MHD oscillations in an inhomogeneous magnetoplasma

1990 ◽  
Vol 44 (2) ◽  
pp. 361-375 ◽  
Author(s):  
Andrew N. Wright
Keyword(s):  
Magnetic Field ◽  
Wave Equation ◽  
Density Distribution ◽  
Cold Plasma ◽  
Wave Equations ◽  
Perturbation Field ◽  
Plasma Density Distribution ◽  
Background Magnetic Field ◽  
Transverse Fields ◽  
The Magnetic Field

In a cold plasma the wave equation for solely compressional magnetic field perturbations appears to decouple in any surface orthogonal to the background magnetic field. However, the compressional fields in any two of these surfaces are related to each other by the condition that the perturbation field b be divergence-free. Hence the wave equations in these surfaces are not truly decoupled from one another. If the two solutions happen to be ‘matched’ (i.e. V.b = 0) then the medium may execute a solely compressional oscillation. If the two solutions are unmatched then transverse fields must evolve. We consider two classes of compressional solutions and derive a set of criteria for when the medium will be able to support pure compressional field oscillations. These criteria relate to the geometry of the magnetic field and the plasma density distribution. We present the conditions in such a manner that it is easy to see if a given magnetoplasma is able to executive either of the compressional solutions we investigate.

scholarly journals Spacecraft and interplanetary contributions to the magnetic environment on-board LISA Pathfinder

2020 ◽  
Vol 494 (2) ◽  
pp. 3014-3027
Author(s):  
M Armano ◽  
H Audley ◽  
J Baird ◽  
P Binetruy ◽  
M Born ◽  
...  
Keyword(s):  
Magnetic Field ◽  
New Technologies ◽  
Magnetic Measurements ◽  
Magnetic Measurement ◽  
Low Frequency ◽  
Lisa Pathfinder ◽  
Frequency Regime ◽  
The Magnetic Field ◽  
Instrument Sensitivity ◽  
Stationary Component

ABSTRACT LISA Pathfinder (LPF) has been a space-based mission designed to test new technologies that will be required for a gravitational wave observatory in space. Magnetically driven forces play a key role in the instrument sensitivity in the low-frequency regime (mHz and below), the measurement band of interest for a space-based observatory. The magnetic field can couple to the magnetic susceptibility and remanent magnetic moment from the test masses and disturb them from their geodesic movement. LPF carried on-board a dedicated magnetic measurement subsystem with noise levels of 10 $\rm nT \ Hz^{-1/2}$ from 1 Hz down to 1 mHz. In this paper we report on the magnetic measurements throughout LPF operations. We characterize the magnetic environment within the spacecraft, study the time evolution of the magnetic field and its stability down to 20 μHz, where we measure values around 200 $\rm nT \ Hz^{-1/2}$, and identify two different frequency regimes, one related to the interplanetary magnetic field and the other to the magnetic field originating inside the spacecraft. Finally, we characterize the non-stationary component of the fluctuations of the magnetic field below the mHz and relate them to the dynamics of the solar wind.

scholarly journals ANALYSIS OF HIGH-FREQUENCY C-CORE MAGNETIC FLUX LEAKAGES FOR BONE TUMOR WITH INDUCTION HEATING BY USING MULTI-COIL

2019 ◽  
Author(s):  
Metharak Jokpudsa ◽  
Supawat Kotchapradit ◽  
Chanchai Thongsopa ◽  
Thanaset Thosdeekoraphat
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Tumor Tissue ◽  
Low Frequency ◽  
Heat Energy ◽  
High Frequencies ◽  
Frequency Magnetic Field ◽  
High Frequency Magnetic Field ◽  
The Magnetic Field ◽  
Flux Leakage

High-frequency magnetic field has been developed pervasively. The induction of heat from the magnetic field can help to treat tumor tissue to a certain extent. Normally, treatment by the low-frequency magnetic field needed to be combined with magnetic substances. To assist in the induction of magnetic fields and reduce flux leakage. However, there are studies that have found that high frequencies can cause heat to tumor tissue. In this paper present, a new magnetic application will focus on the analysis of the high-frequency magnetic nickel core with multi-coil. In order to focus the heat energy using a high-frequency magnetic field into the tumor tissue. The magnetic coil was excited by 915 MHz signal and the combination of tissues used are muscle, bone, and tumor. The magnetic power on the heating predicted by the analytical model, the power loss density (2.98e-6 w/m3) was analyzed using the CST microwave studio.

scholarly journals Practice and perspectives of using ultrasensitive magnetometers in biomedical research.

2021 ◽  
Author(s):  
Yu.V. Maslennikov ◽  
◽  
◽  
Keyword(s):  
Magnetic Field ◽  
Biomedical Research ◽  
Magnetic Measurements ◽  
Signal To Noise Ratio ◽  
Frequency Range ◽  
Optically Pumped ◽  
Technical Solutions ◽  
Further Development ◽  
The Magnetic Field

There are a large number of sensors for measuring the magnetic field of biological objects. They are characterized by the type of the measured physical parameter (magnetic field strength, magnetic flux, etc.), the level of intrinsic sensitivity, and the frequency range of the recorded signals. The long-term practice of studying biomagnetic signals shows that only SQUID-based magnetometers and optically pumped magnetometers have sensitivity levels sufficient for recording biomagnetic signals with the required signal-to-noise ratio. This chapter reflects the main directions of using such magnetometers and methods of magnetic measurements in biomedical research, gives examples of existing technical solutions, and shows possible ways of their further development.

Low Frequency Measurements in Amorphous Wire for Studying GMI Effect

2011 ◽  
Vol 495 ◽  
pp. 201-204
Author(s):  
Polykseni Vourna
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
Major Change ◽  
Wheatstone Bridge ◽  
Amorphous Wire ◽  
Dc Voltage ◽  
Gmi Effect ◽  
Offset Voltage ◽  
Ac Current ◽  
The Magnetic Field

When a soft ferromagnetic material is flown by an ac current and a magnetic field is applied at the same time, a major change of its impedance is occurred. The aim of this paper is to investigate the influence of low frequency (1KHz-12KHz) ac current and the applied magnetic field on an amorphous magnetic wire (Co68Fe4.35Si12.5B15) without glass coating. For this purpose an experimental configuration has been setup, based on a Wheatstone bridge which receives an ac input signal from a frequency generator. The output is connected to the amorphous wire wrapped with a coil supplied by a dc voltage for the generation of the magnetic field. The output voltage pulse is measured for two cases a) The value of ac frequency is changing while the value of dc voltage applied to the coil remains constant (the magnetic field remains unchanged) and b) the magnetic field is changing while the ac frequency remains constant to a predefined value. Experimental results of the first scenario showed that when the frequency is altered a non-linear increase of the ac signal is observed at the output which shows an increase of the GMI effect and is related to the non-linearity of the wire’s permeability. For the second scenario the results showed an increase of the output signal offset (voltage) which also indicates an increase of the GMI effect.

scholarly journals Less Is Enough: Assessment of the Random Sampling Method for the Analysis of Magnetoencephalography (MEG) Data

2019 ◽  
Vol 24 (4) ◽  
pp. 98
Author(s):  
Cristina Campi ◽  
Annalisa Pascarella ◽  
Francesca Pitolli
Keyword(s):  
Magnetic Field ◽  
Random Sampling ◽  
Sampling Method ◽  
Brain Activity ◽  
Memory Storage ◽  
Non Invasive ◽  
Regularization Techniques ◽  
Ill Posed ◽  
The Brain ◽  
The Magnetic Field

Magnetoencephalography (MEG) aims at reconstructing the unknown neuroelectric activity in the brain from non-invasive measurements of the magnetic field induced by neural sources. The solution of this ill-posed, ill-conditioned inverse problem is usually dealt with using regularization techniques that are often time-consuming, and computationally and memory storage demanding. In this paper we analyze how a slimmer procedure, random sampling, affects the estimation of the brain activity generated by both synthetic and real sources.

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