Metastabile Deformationen in nematischen flüssigen Kristallen / Metastable Deformations in Nematic Liquid Crystals

1974 ◽  
Vol 29 (2) ◽  
pp. 310-318
Author(s):  
G. Heppke ◽  
F. Schneider
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Experimental Studies ◽  
Conductivity Measurements ◽  
Elastic Deformations ◽  
The Magnetic Field ◽  
Good Agreement

The magnetic field induced elastic deformations of nematic liquid crystals are studied theoretically. In accordance with the theory of Dafermos, two types of elastic deformations are predicted which differ in energy. The properties of the metastable deformations are discussed in detail. Experimental studies have been performed on MBBA using electrical conductivity measurements. Metastable deformations are obtained after rotating the direction of the magnetic field by more than 90° with respect to the direction of the homeotropically aligned sample. The observed conductivity values are in good agreement with theory.

A DYNAMICAL METHOD FOR DETERMINING THE ELASTIC CONSTANTS AND RELAXATION PARAMETERS IN NEMATIC LIQUID CRYSTALS

2000 ◽  
Vol 14 (04) ◽  
pp. 139-146 ◽  
Author(s):  
EMIL PETRESCU ◽  
CORNELIA MOTOC ◽  
DOINA MANAILA
Keyword(s):  
Magnetic Field ◽  
Liquid Crystals ◽  
Elastic Constants ◽  
Light Transmission ◽  
Nematic Liquid Crystals ◽  
Relaxation Parameters ◽  
Nematic Director ◽  
Dynamical Method ◽  
The Magnetic Field ◽  
Good Agreement

The theoretical model proposed by Pieranski et al.3 to describe the phenomena occurring in nematic liquid crystals when the magnetic field is suddenly varied was extended by considering higher powers of the distortion angle for the nematic director. Equations giving the time evolution of the number of extinctions in the light transmission were obtained. These equations depend on some relaxation parameters (the time constants τA and τB intervening when the magnetic field was switched "on" or "off", respectively) and on the ratio of elastic constants. The equations were solved numerically and good agreement with the experimental data was obtained for the nematic MBBA.

scholarly journals The Influence of Single-Walled Carbon Nanotubes on the Dynamic Properties of Nematic Liquid Crystals in Magnetic Field

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4031 ◽  
Author(s):  
Cirtoaje ◽  
Petrescu
Keyword(s):  
Magnetic Field ◽  
Liquid Crystals ◽  
Dynamic Properties ◽  
Relaxation Times ◽  
Continuum Theory ◽  
Elastic Continuum ◽  
Walled Carbon Nanotubes ◽  
The Impact ◽  
The Magnetic Field ◽  
Good Agreement

This article aims to study the impact of carbon nanotube dispersions in liquid crystals. A theoretical model for the system’s dynamics is presented, considering the elastic continuum theory and a planar alignment of liquid crystal molecules on the nanotube’s surface. Experimental calculation of the relaxation times in the magnetic field was made for two cases: when the field was switched on (τon), and when it was switched off (τoff). The results indicate an increase of the relaxation time by about 25% when the magnetic field was switched off, and a smaller increase (about 10%) when the field was switched on, where both were in good agreement with the theoretical values.

scholarly journals Electric explosion of flat copper conductors in asymmetric and symmetric configurations in the current skinning mode

2021 ◽  
Vol 2064 (1) ◽  
pp. 012028
Author(s):  
N A Labetskaya ◽  
I M Datsko ◽  
S A Chaikovsky ◽  
V A Vankevich ◽  
E V Oreshkin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Experimental Studies ◽  
Longitudinal Axis ◽  
Plasma Formation ◽  
Conductor Surface ◽  
Key Issues ◽  
Energy Transportation ◽  
The Magnetic Field ◽  
Asymmetric Configuration ◽  
Good Agreement

Abstract Plasma formation on the surface of conductors as a result of a skin explosion is one of the key issues of the efficiency of energy transportation along the vacuum lines of terawatt-level pulsed generators. Experimental studies of plasma formation on the surface of flat conductors were carried out on the MIG generator (current level ~ 2.5 MA, rise time ~ 100 ns). The magnitude of the magnetic field induction exceeded the values required for the explosion of the conductor surface facing the magnetic field in an asymmetric configuration or both surfaces of the conductor in a symmetric configuration. It was shown that in both configurations, a plasma channel is formed on the surface of a copper foil with a thickness of 100 microns along its longitudinal axis. Experimental data on the dynamics of plasma formation at the edges of a flat conductor have been obtained. A magnetohydrodynamic simulation of an explosion in strong magnetic fields of flat conductors whose width is much greater than their thickness showed that: the expansion of the plasma along the width of the conductor is suppressed, and the plasma expands mainly along its thickness. The simulation results are in good agreement with the experimental once.

Investigating flexible textile-based coils for wireless charging wearable electronics

2019 ◽  
Vol 50 (3) ◽  
pp. 333-345 ◽  
Author(s):  
Danmei Sun ◽  
Meixuan Chen ◽  
Symon Podilchak ◽  
Apostolos Georgiadis ◽  
Qassim S Abdullahi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Electromagnetic Field ◽  
Electric Field ◽  
Dimensional Stability ◽  
Screen Printing ◽  
Wearable Electronics ◽  
Wireless Charging ◽  
The Magnetic Field ◽  
Screen Printed

Smart and interactive textiles have been attracted great attention in recent years. This research explored three different techniques and processes in developing textile-based conductive coils that are able to embed in a garment layer. Coils made through embroidery and screen printing have good dimensional stability, although the resistance of screen printed coil is too high due to the low conductivity of the print ink. Laser cut coil provided the best electrical conductivity; however, the disadvantage of this method is that it is very difficult to keep the completed coil to the predetermined shape and dimension. The tested results show that an electromagnetic field has been generated between the textile-based conductive coil and an external coil that is directly powered by electricity. The magnetic field and electric field worked simultaneously to complete the wireless charging process.

scholarly journals Hydromagnetic dynamos in rotating spherical fluid shells in dependence on the Prandtl number, density stratification and electromagnetic boundary conditions

2014 ◽  
Vol 44 (4) ◽  
pp. 293-312 ◽  
Author(s):  
Tomáš Šoltis ◽  
Ján Šimkanin
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Magnetic Fields ◽  
Prandtl Number ◽  
Inner Core ◽  
Polar Regions ◽  
Number Density ◽  
Magnetic Diffusion ◽  
Spherical Fluid ◽  
The Magnetic Field

Abstract We present an investigation of dynamo in a simultaneous dependence on the non-uniform stratification, electrical conductivity of the inner core and the Prandtl number. Computations are performed using the MAG dynamo code. In all the investigated cases, the generated magnetic fields are dipolar. Our results show that the dynamos, especially magnetic field structures, are independent in our investigated cases on the electrical conductivity of the inner core. This is in agreement with results obtained in previous analyses. The influence of non-uniform stratification is for our parameters weak, which is understandable because most of the shell is unstably stratified, and the stably stratified region is only a thin layer near the CMB. The teleconvection is not observed in our study. However, the influence of the Prandtl number is strong. The generated magnetic fields do not become weak in the polar regions because the magnetic field inside the tangent cylinder is always regenerated due to the weak magnetic diffusion.

Doppler-Shifted Cyclotron Resonance in Thin Metal Films

1972 ◽  
Vol 50 (18) ◽  
pp. 2122-2137
Author(s):  
R. Turner ◽  
J. F. Cochran
Keyword(s):  
Magnetic Field ◽  
Metal Films ◽  
Thin Metal Film ◽  
Thin Metal ◽  
Free Electrons ◽  
Fermi Surfaces ◽  
First Order ◽  
Simple Quantum ◽  
The Magnetic Field ◽  
Good Agreement

According to Van Gelder the microwave absorption by a thin metal film in the presence of a static magnetic field normal to the film contains a series of peaks as the magnetic field is varied. In the present paper it is argued that these peaks correspond to Doppler-shifted cyclotron resonances of the carriers in the metal due to the quantization of electron momenta normal to the plane of the film. A simple quantum calculation is presented for the case of free electrons where the film is thin enough that to first order the microwave fields within are determined only by the boundary conditions and Maxwell's equations. The quantum expression is in good agreement with the absorption calculated using semiclassical arguments which can be readily extended to more complicated Fermi surfaces.

Dry-friction and critical state in lyotropic nematic liquid crystals in a magnetic field

1996 ◽  
Vol 222 (1-2) ◽  
pp. 113-118 ◽  
Author(s):  
E. Andreoli de Oliveira ◽  
G. Barbero ◽  
A.M. Figueiredo Neto ◽  
A.K. Zvezdin
Keyword(s):  
Magnetic Field ◽  
Liquid Crystals ◽  
Critical State ◽  
Dry Friction ◽  
Nematic Liquid Crystals
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