scholarly journals The Freedericksz Transition in a Spatially Varying Magnetic Field

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 541
Author(s):  
Tianyi Guo ◽  
Xiaoyu Zheng ◽  
Peter Palffy-Muhoray
Keyword(s):  
Magnetic Field ◽  
Cylindrical Symmetry ◽  
Central Plane ◽  
Freedericksz Transition ◽  
Radial Magnetic Field ◽  
Director Field ◽  
Electric And Magnetic Fields ◽  
Fréedericksz Transition ◽  
Spatially Varying ◽  
The Magnetic Field

Much is known about the Freedericksz transition induced by uniform electric and magnetic fields in nematic liquid crystals. In this work, we are interested in the effects of a spatially varying field on the transition. Specifically, we study the director configuration in a homeotropic nematic cell in a spatially varying magnetic field with cylindrical symmetry. The experiment is conducted with a ring magnet which provides a radial magnetic field with magnitude monotonically decreasing to zero at the center. The nematic cell is positioned in the central plane of the ring, with the cell normal parallel to the ring normal. Interference patterns of the nematic cell between crossed polarizers were observed. The director configuration in the nematic cell is modeled with Frank–Oseen theory, and the computed interference pattern from the simulated director field are compared with experiment. We conclude that if the magnetic field strength varies with position in the plane of the cell, there is no Freedericksz transition.

scholarly journals Magnetic segregation effect in liquid crystals doped with carbon nanotubes

2019 ◽  
Vol 10 ◽  
pp. 1464-1474 ◽  
Author(s):  
Danil A Petrov ◽  
Pavel K Skokov ◽  
Alexander N Zakhlevnykh ◽  
Dmitriy V Makarov
Keyword(s):  
Magnetic Field ◽  
Carbon Nanotubes ◽  
Liquid Crystal ◽  
Phase Lag ◽  
Freedericksz Transition ◽  
Planar Texture ◽  
Segregation Effect ◽  
Fréedericksz Transition ◽  
The Magnetic Field ◽  
Crystal Composite

We study the orientational transitions in a suspension of carbon nanotubes in a nematic liquid crystal induced by an external magnetic field. The case of a finite orientational anchoring of liquid crystal molecules at the surface of doped carbon nanotubes is considered. It is shown that in a magnetic field the initial homogeneous planar texture of the liquid crystal–carbon nanotubes mixture is disturbed in a threshold manner (Fréedericksz transition). The orientational and concentration distributions of the suspension are studied for different values of the magnetic field strength and segregation intensity of the impurity subsystem. The optical phase lag between ordinary and extraordinary rays of light transmitted through a layer of a liquid crystal composite is calculated. The possibility of changing the nature of the Fréedericksz transition from second order to first order is shown. This tricritical behavior is related to the redistribution of the carbon nanotubes (segregation effect) inside the layer.

Transmission line sanitary protective zones. Electromagnetic safety problems

2020 ◽  
pp. 736-736
Author(s):  
N. B. Rubtsova ◽  
A. Y. Tokarskiy
Keyword(s):  
Magnetic Field ◽  
Risk Factor ◽  
Transmission Lines ◽  
General Public ◽  
Field Component ◽  
Regulatory Requirements ◽  
Protection Zones ◽  
Electric And Magnetic Fields ◽  
Health Risk Factor ◽  
The Magnetic Field

The main problems of overhead and cable transmission lines with voltage >=110 kV electric and magnetic fields general public protection are presented. It is shown that it is necessary to develop regulatory requirements for these lines’ sanitary protection zones organization, taking into account the magnetic field component, because its possible health risk factor, up to carcinogenic.

Optical Fréedericksz transition and director field structure recording in dye-doped nematic liquid-crystalline polymer

2019 ◽  
Vol 276 ◽  
pp. 275-281 ◽  
Author(s):  
Ivan Budagovsky ◽  
Aleksey Kuznetsov ◽  
Sergey Shvetsov ◽  
Mikhail Smayev ◽  
Alexander Zolot'ko ◽  
...  
Keyword(s):  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
Field Structure ◽  
Freedericksz Transition ◽  
Director Field ◽  
Fréedericksz Transition

scholarly journals Fréedericksz transition in a periodic magnetic field

1988 ◽  
Vol 38 (5) ◽  
pp. 2641-2649 ◽  
Author(s):  
M. C. Torrent ◽  
F. Sagués ◽  
F. Arias ◽  
M. San Miguel
Keyword(s):  
Magnetic Field ◽  
Freedericksz Transition ◽  
Periodic Magnetic Field ◽  
Fréedericksz Transition

Optimization of magnetic hat for quartz flexible accelerometer

Sensor Review ◽  
2016 ◽  
Vol 36 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Cuo Wang ◽  
Xingfei Li ◽  
Ke Kou ◽  
Chunguo Long
Keyword(s):  
Magnetic Field ◽  
Field Distribution ◽  
Cylindrical Symmetry ◽  
Air Gap ◽  
Magnetic Sensors ◽  
Magnetic Field Distribution ◽  
Navigation Systems ◽  
Pole Piece ◽  
Content Type ◽  
The Magnetic Field

Purpose – This study aims to ameliorate the strength and uniformity of the magnetic field in the air-gap of quartz flexible accelerometers. Quartz flexible accelerometers (QFAs), a type of magneto-electric inertial sensors, have wide applications in inertial navigation systems, and their precision, linearity and stability performance are largely determined by the magnetic field in operation air-gap. To enhance the strength and uniformity of the magnetic field in the air-gap, a magnetic hat structure has been proposed to replace the traditional magnetic pole piece which tends to produce stratiform magnetic field distribution. Design/methodology/approach – Three-dimensional analysis in ANSYS workbench helps to exhibit magnetic field distribution for the structures with a pole piece and a magnetic hat, and under the hypothesis of cylindrical symmetry, two-dimensional finite element optimization by ANSYS APDL gives an optimal set of dimensions of the magnetic hat. Findings – Three structures of the QFA with a pole piece, a non-optimized magnetic hat and an optimized magnetic hat are compared by the simulation in ANSYS Maxwell and experiments measuring the electromagnetic rebalance force. The results show that the optimized hat can supply stronger and more uniform magnetic field, which is reflected by larger and more linear rebalance force. Originality/value – To the authors ' knowledge, the magnetic hat and its dimension optimization have rarely been reported, and they can find significant applications in designing QFAs or other similar magnetic sensors.

Development of a database of Jovian magnetodisc crossings by Galileo and Juno spacecraft from magnetometer data

2020 ◽  
Author(s):  
Igor Alekseev ◽  
Elena Belenkaya ◽  
Alexander Lavrukhin ◽  
David Parunakian ◽  
Ivan Pensionerov
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Polar Axis ◽  
Dipole Axis ◽  
Radial Magnetic Field ◽  
Jovian Magnetosphere ◽  
Central Surface ◽  
Magnetometer Data ◽  
Plasma Measurements ◽  
The Magnetic Field

<p>Jovian magnetosphere has   a huge equatorial plasma disk, which is also known as the current sheet or magnetodisk. This current sheet enlarges the subsolar magnetosphere size more than twice compare to purely planetary dipole magnetosphere. Near to the planet   the magnetodisk is aligned with the magnetic equatorial plane. As consequence of the dipole axis tilted to the polar axis about 10, each of Juno orbits crossed the central surface of the disk current two times during one jovian day (9, 92 hours). Finally, we have  about 1725 current sheet crossings to study the plasma sheet and current sheets structure.</p> <p>In our work we have developed a database of Jovian current sheet crossings, performed by Galileo and Juno spacecraft, which includes magnetic field and plasma measurements. Current sheet crossings were determined using magnetometer data in distant magnetosphere as a region with the magnetic field strength less than the dipole value at the same point and central current sheet position have been marked by boundary between the region with opposite signum of the radial magnetic field component.</p>

Considerations of the effect of space-charge in the magnetron

1940 ◽  
Vol 36 (1) ◽  
pp. 94-100 ◽  
Author(s):  
E. B. Moullin
Keyword(s):  
Magnetic Field ◽  
Space Charge ◽  
Cylindrical Symmetry ◽  
Potential Difference ◽  
Anode Current ◽  
Pronounced Decrease ◽  
Field Parallel ◽  
Image Position ◽  
The Magnetic Field

When a diode thermionic tube, having cylindrical symmetry, is placed in a magnetic field parallel to its axis it is commonly called a magnetron. If there is a given potential difference between the anode and cathode of the tube, and if the magnetic field is steadily increased, a sharp and pronounced decrease of anode current occurs when the field reaches a certain value. It is easy to show that, if electrons leave without velocity from a cathode of radius b, they will just graze a concentric anode of radius a at potential V when the magnetic field H has the value given by

Investigation of DC Vacuum Arc Interruption Ability with Combined Axial and Radial Magnetic Field

2012 ◽  
Vol 516-517 ◽  
pp. 1791-1797 ◽  
Author(s):  
Mohmmad Al Dweikat ◽  
Yu Long Huang ◽  
Xiao Lin Shen ◽  
Wei Dong Liu
Keyword(s):  
Magnetic Field ◽  
Axial Magnetic Field ◽  
Vacuum Arc ◽  
Axial Component ◽  
Circuit Breakers ◽  
Radial Magnetic Field ◽  
Vacuum Interrupter ◽  
Magnetic Field Simulation ◽  
The Magnetic Field ◽  
Field Influence

DC Vacuum Circuit Breakers based arc control has been a major topic in the last few decades. Understanding vacuum arc (VA) gives the ability to improve vacuum circuit breakers capacity. In this paper, the interaction of a DC vacuum arc with a combined Axial-Radial magnetic field was investigated. The proposed system contains an external coil to produce axial magnetic field (AMF) across the vacuum chamber. The vacuum interrupter (VI) contacts were assumed to be untreated radial magnetic field (RMF) contacts. For this purpose, Finite Element Method (FEM) based Multiphysics simulation of the immerging magnetic field influence on the VA is presented. The simulation shown the ability of the presented system to deflect high DC vacuum arc, also reveals that the vacuum arc interruption capability increases with the rise of the axial component of the magnetic field. Simulation results shown that this method can be applied to improve the interruption capability of the VI.

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