COMPARISON OF CARDIAC MAGNETIC FIELD DISTRIBUTIONS DURING DEPOLARIZATION AND  REPOLARIZATION

Multichannel magnetocardiography measures the magnetic field distribution of the human heart noninvasively from many sites over the body surface. Multichannel magnetocardiogram (MCG) analysis enables regional temporal differences in the distribution of cardiac magnetic field strength during depolarization and repolarization to be identified, allowing estimation of the global and local inhomogeneity of the cardiac activation process. The aim of this study was to compare the spatial distribution of cardiac magnetic field strength during ventricular depolarization and repolarization in both normal subjects and patients with cardiac abnormalities, obtaining amplitude measurements by magnetocardiography. MCGs were recorded at 49 sites over the heart from three normal subjects and two patients with inverted T-wave conditions. The magnetic field intensity during depolarization and repolarization was measured automatically for each channel and displayed spatially as contour maps. A Pearson correlation was used to determine the spatial relationship between the variables. For normal subjects, magnetic field strength maps during depolarization (R-wave) showed two asymmetric regions of magnetic field strength with a high positive value in the lower half of the chest and a high negative value above this. The regions of high R-wave amplitude corresponded spatially to concentrated asymmetric regions of high magnetic field strength during repolarization (T-wave). Pearson-r correlation coefficients of 0.7 (p<0.01), 0.8 (p<0.01) and 0.9 (p<0.01) were obtained from this analysis for the three normal subjects. A negative correlation coefficient of -0.7 (p<0.01) was obtained for one of the subjects with inverted T-wave abnormalities, suggesting similar but inverted magnetic field and current distributions to normal subjects. Even with the high correlation values in these four subjects, the MCG was able to identify differences in the distribution of magnetic field strength, with a shift in the T-wave relative to the R-wave. The measurement of cardiac magnetic field distribution during depolarization and repolarization of normal subjects and patients with clinical abnormalities should enable the improvement of theoretical models for the explanation of the cardiac depolarization and repolarization processes.

Download Full-text

Research on Magnetic Field Distribution and Characteristics of a 3.7 kW Wireless Charging System for Electric Vehicles under Offset

Energies ◽

10.3390/en12030392 ◽

2019 ◽

Vol 12 (3) ◽

pp. 392 ◽

Cited By ~ 6

Author(s):

Li Zhai ◽

Guangyuan Zhong ◽

Yu Cao ◽

Guixing Hu ◽

Xiang Li

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Field Distribution ◽

Electric Vehicles ◽

Magnetic Field Distribution ◽

Wireless Charging ◽

Charging System ◽

Physical Prototype ◽

The Magnetic Field

A 3.7 kW resonant wireless charging system (WCS) is proposed to realize the energy transmission for electric vehicles. In addition to designing the electrical modules functionally, coupling coils are designed and verified by physical prototype, which guarantees the accuracy of coils and subsequent simulations. Then, we focus on the magnetic field distribution of coupling coils in the vehicle environment. Four points (A1, A2, A3, A4) in different regions and three points (the head B1, chest B2 and cushion B3) in the driving seat are helped to measure the magnetic field strength. The magnetic field distribution of coils under five offsets of 60 mm, 120 mm, 180 mm, 240 mm and 300 mm are analyzed theoretically and simulated correspondingly. The simulation results indicate that the magnetic field strength of test points are within the limits, but the strength at A3 is larger than 30.4 A/m required by SAE J2954 at 40% offset and 50% offset. Taking into account the composition of the actual magnetic field, the magnetic field distribution due to side-band and odd harmonic current are also obtained. An experimental bench for the proposed 3.7 kW WCS is built to validate the rightness and feasibility of the simulated scheme. The results of simulation and experiments of magnetic field distribution have less error and are often in good agreement.

Download Full-text

Study and Modeling of the Magnetic Field Distribution in the Fricker Hydrocyclone Cylindrical Part

Computation ◽

10.3390/computation8020042 ◽

2020 ◽

Vol 8 (2) ◽

pp. 42 ◽

Cited By ~ 1

Author(s):

Boris Avdeev ◽

Roman Dema ◽

Sergei Chernyi

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Field Distribution ◽

Magnetic Force ◽

Cylindrical Part ◽

Magnetic Field Distribution ◽

Radial Magnetic Field ◽

Working Chamber ◽

The Magnetic Field

The magnetic field distribution along the radius and height in the working chamber of a hydrocyclone with a radial magnetic field is studied. One of the most important parameters of magnetic hydrocyclones is the magnetic field distribution along the radius and height of the working chamber. It is necessary for calculating the coagulation forces and the magnetic force affecting the particle or flocculus. The magnetic field strength was calculated through magnetic induction, measured by a teslameter at equal intervals and at different values of the supply DC current. The obtained values for the magnetic field strength are presented in the form of graphs. The field distribution curves produced from the dependences found earlier were constructed. The correlation coefficients were calculated. It was proven that the analyzed dependences could be used in further calculations of coagulation forces and magnetic force, because theoretical and experimental data compared favourably with each other. The distribution along the radius and height in the cylindrical part of the magnetic hydrocyclone was consistent with data published in the scientific literature.

Download Full-text

Mathematical modeling of electromagnetic environment at railroad junctions

E3S Web of Conferences ◽

10.1051/e3sconf/20199101010 ◽

2019 ◽

Vol 91 ◽

pp. 01010

Author(s):

Natalya Buyakova ◽

Vasiliy Zakaryukin ◽

Andrey Kryukov

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Field Distribution ◽

Rolling Stock ◽

Electromagnetic Environment ◽

Environment Modeling ◽

Underground Pipelines ◽

Magnetic Strength ◽

The Magnetic Field

Results of computer-aided studies of electromagnetic environment at railroad junctions of alternating current electrified railroads having voltage of 25 kV are presented. A large number of lines and overhead catenaries significantly complicate the picture of electromagnetic field distribution. The nature of the field distribution in space is significantly affected by the rolling stock on station tracks. Besides, the task of electromagnetic environment modeling is complicated by the presence of underground pipelines and enclosures, and reinforced concrete passenger platforms. During the transfer of power of 10 + j10 MV·A through the junction of overhead system, the magnetic field strength at a level of 1,8 m is considerably less than the magnetic strength at a railway haul due to current distribution on overhead system of several tracks. Magnetic field strength levels in calculation examples do not exceed amplitude of 30 A/m. The train performance leads to changes in the strengths of the electrical and magnetic fields. The dynamics of changes is presented as a result of simulation modeling of train movement modes.

Download Full-text

Optimization of a Two-Layer 3D Coil Structure with Uniform Magnetic Field

Wireless Power Transfer ◽

10.1155/2021/6303628 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Davor Vinko ◽

Domagoj Bilandžija ◽

Vanja Mandrić Radivojević

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Field Distribution ◽

Uniform Magnetic Field ◽

Optimization Method ◽

Magnetic Field Distribution ◽

Wireless Power ◽

Average Magnetic Field ◽

Coil Structure

Conventional magnetically coupled resonant wireless power transfer systems are faced with resonant frequency splitting phenomena and impedance mismatch when a receiving coil is placed at misaligned position. These problems can be avoided by using uniform magnetic field distribution at receiving plane. In this paper, a novel 3D transmitting coil structure with improved uniform magnetic field distribution is proposed based on a developed optimization method. The goal is to maximize the average magnetic field strength and uniform magnetic field section of the receiving plane. Hence, figures of merit (FoM1 and FoM2) are introduced and defined as product of average magnetic field strength and length or surface along which uniform magnetic field is generated, respectively. The validity of the optimization method is verified through laboratory measurements performed on the fabricated coils driven by signal generator at operating frequency of 150 kHz. Depending on the allowed ripple value and predefined coil proportions, the proposed transmitting coil structure gives the uniform magnetic field distribution across 50% to 90% of the receiving plane.

Download Full-text

ALMA reveals the magnetic field evolution in the high-mass star forming complex G9.62+0.19

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834100 ◽

2019 ◽

Vol 626 ◽

pp. A36 ◽

Cited By ~ 6

Author(s):

D. Dall’Olio ◽

W. H. T. Vlemmings ◽

M. V. Persson ◽

F. O. Alves ◽

H. Beuther ◽

...

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

High Mass ◽

Mass Star ◽

Evolutionary Sequence ◽

Star Forming ◽

High Magnetic Field Strength ◽

The Magnetic Field ◽

Linear Polarisation

Context. The role of magnetic fields during the formation of high-mass stars is not yet fully understood, and the processes related to the early fragmentation and collapse are as yet largely unexplored. The high-mass star forming region G9.62+0.19 is a well known source, presenting several cores at different evolutionary stages. Aims. We seek to investigate the magnetic field properties at the initial stages of massive star formation. We aim to determine the magnetic field morphology and strength in the high-mass star forming region G9.62+0.19 to investigate its relation to the evolutionary sequence of the cores. Methods. We made use of Atacama Large Millimeter Array (ALMA) observations in full polarisation mode at 1 mm wavelength (Band 7) and we analysed the polarised dust emission. We estimated the magnetic field strength via the Davis–Chandrasekhar–Fermi and structure function methods. Results. We resolve several protostellar cores embedded in a bright and dusty filamentary structure. The polarised emission is clearly detected in six regions: two in the northern field and four in the southern field. Moreover the magnetic field is orientated along the filament and appears perpendicular to the direction of the outflows. The polarisation vectors present ordered patterns and the cores showing polarised emission are less fragmented. We suggest an evolutionary sequence of the magnetic field, and the less evolved hot core exhibits a stronger magnetic field than the more evolved hot core. An average magnetic field strength of the order of 11 mG was derived, from which we obtain a low turbulent-to-magnetic energy ratio, indicating that turbulence does not significantly contribute to the stability of the clump. We report a detection of linear polarisation from thermal line emission, probably from methanol or carbon dioxide, and we tentatively compared linear polarisation vectors from our observations with previous linearly polarised OH masers observations. We also compute the spectral index, column density, and mass for some of the cores. Conclusions. The high magnetic field strength and smooth polarised emission indicate that the magnetic field could play an important role in the fragmentation and the collapse process in the star forming region G9.62+019 and that the evolution of the cores can be magnetically regulated. One core shows a very peculiar pattern in the polarisation vectors, which can indicate a compressed magnetic field. On average, the magnetic field derived by the linear polarised emission from dust, thermal lines, and masers is pointing in the same direction and has consistent strength.

Download Full-text

"In Situ" Evaluation of Ferromagnetic Bodies Magnetic Characteristics

Materials Science Forum ◽

10.4028/www.scientific.net/msf.792.177 ◽

2014 ◽

Vol 792 ◽

pp. 177-182 ◽

Cited By ~ 3

Author(s):

Horia Gavrila ◽

Marilena Stanculescu ◽

Mihai Maricaru ◽

Marian Vasilescu ◽

Paul Andrei ◽

...

Keyword(s):

Magnetic Field ◽

Field Distribution ◽

Magnetic Induction ◽

The Body ◽

Magnetic Field Distribution ◽

Magnetic Characteristics ◽

Field Problem ◽

Ill Posed ◽

The Magnetic Field

The B-H characteristic of an iron body material influences the magnetic field measured in the air. On principle, one can pose the problem of B-H relation determination, by making measurements of the magnetic induction in the neighbourhood of the body. Unfortunately, we have an ill-posed inverse magnetic field problem, for which there is possible that, big variations of the BH characteristic to produce only very small modifications of the magnetic field in the air. It is essential to use a sufficiently sensitive computation procedure in order to produce credible results. This paper proposes a device for the B-H characteristic evaluation, admitting that inside the ferromagnetic bodies the magnetic field distribution is not uniform.

Download Full-text

On the Configuration of the Magnetic Field of β CrB

International Astronomical Union Colloquium ◽

10.1017/s0252921100080933 ◽

1976 ◽

Vol 32 ◽

pp. 613-622

Author(s):

I.A. Aslanov ◽

Yu.S. Rustamov

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Radial Velocity ◽

Magnetic Field Strength ◽

Complex Shape ◽

Rotation Period ◽

Field Variation ◽

Magnetic Field Variation ◽

Secular Variations ◽

The Magnetic Field

SummaryMeasurements of the radial velocities and magnetic field strength of β CrB were carried out. It is shown that there is a variability with the rotation period different for various elements. The curve of the magnetic field variation measured from lines of 5 different elements: FeI, CrI, CrII, TiII, ScII and CaI has a complex shape specific for each element. This may be due to the presence of magnetic spots on the stellar surface. A comparison with the radial velocity curves suggests the presence of a least 4 spots of Ti and Cr coinciding with magnetic spots. A change of the magnetic field with optical depth is shown. The curve of the Heffvariation with the rotation period is given. A possibility of secular variations of the magnetic field is shown.

Download Full-text

The effects of magnetic field strength on the properties of wind generated from hot accretion flow

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832985 ◽

2018 ◽

Vol 615 ◽

pp. A35 ◽

Cited By ~ 10

Author(s):

De-Fu Bu ◽

Amin Mosallanezhad

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Pressure Gradient ◽

Magnetic Field Strength ◽

Magnetic Pressure ◽

Gas Pressure ◽

Accretion Flow ◽

Accretion Flows ◽

Black Hole Accretion ◽

The Magnetic Field

Context. Observations indicate that wind can be generated in hot accretion flow. Wind generated from weakly magnetized accretion flow has been studied. However, the properties of wind generated from strongly magnetized hot accretion flow have not been studied. Aims. In this paper, we study the properties of wind generated from both weakly and strongly magnetized accretion flow. We focus on how the magnetic field strength affects the wind properties. Methods. We solve steady-state two-dimensional magnetohydrodynamic equations of black hole accretion in the presence of a largescale magnetic field. We assume self-similarity in radial direction. The magnetic field is assumed to be evenly symmetric with the equatorial plane. Results. We find that wind exists in both weakly and strongly magnetized accretion flows. When the magnetic field is weak (magnetic pressure is more than two orders of magnitude smaller than gas pressure), wind is driven by gas pressure gradient and centrifugal forces. When the magnetic field is strong (magnetic pressure is slightly smaller than gas pressure), wind is driven by gas pressure gradient and magnetic pressure gradient forces. The power of wind in the strongly magnetized case is just slightly larger than that in the weakly magnetized case. The power of wind lies in a range PW ~ 10−4–10−3 Ṁinc2, with Ṁin and c being mass inflow rate and speed of light, respectively. The possible role of wind in active galactic nuclei feedback is briefly discussed.

Download Full-text

Transport of hyperpolarized samples in dissolution-DNP experiments

Physical Chemistry Chemical Physics ◽

10.1039/c9cp02600b ◽

2019 ◽

Vol 21 (25) ◽

pp. 13696-13705 ◽

Cited By ~ 4

Author(s):

Alexey S. Kiryutin ◽

Bogdan A. Rodin ◽

Alexandra V. Yurkovskaya ◽

Konstantin L. Ivanov ◽

Dennis Kurzbach ◽

...

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Dynamic Nuclear Polarization ◽

Nuclear Polarization ◽

Sample Transfer ◽

The Magnetic Field ◽

Dissolution Dynamic Nuclear Polarization

The magnetic field strength during sample transfer in dissolution dynamic nuclear polarization influences the resulting spectra.

Download Full-text

Zero-Field Level Crossing in the Helium Atom

Canadian Journal of Physics ◽

10.1139/p72-021 ◽

1972 ◽

Vol 50 (2) ◽

pp. 116-118 ◽

Cited By ~ 9

Author(s):

C. W. T. Chien ◽

R. E. Bardsley ◽

F. W. Dalby

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Helium Atom ◽

Cross Sections ◽

Zero Field ◽

Level Crossing ◽

Field Level ◽

Collision Cross Sections ◽

The Magnetic Field

Zero-field level-crossing techniques have been used to measure some upper-state lifetimes of the helium atom. The half-widths of curves obtained by plotting the polarization against the magnetic field strength for the n1D–21D transitions yielded lifetimes of 2.03 × 10−8 s for the 31D state, 3.36 × 10−8 s for the 41D state, and 7.44 × 10−8 s for the 51D state. Collision cross sections for these 1D levels were also determined.

Download Full-text