scholarly journals Self-consistent stationary MHD shear flows in the solar atmosphere as electric field generators

2014 ◽  
Vol 569 ◽  
pp. A44 ◽  
Author(s):  
D. H. Nickeler ◽  
M. Karlický ◽  
T. Wiegelmann ◽  
M. Kraus
Keyword(s):  
Electric Field ◽  
Solar Atmosphere ◽  
Shear Flows ◽  
Self Consistent

A polycrystal hysteresis model for ferroelectric ceramics

2006 ◽  
Vol 462 (2069) ◽  
pp. 1573-1592 ◽  
Author(s):  
Y Su ◽  
G.J Weng
Keyword(s):  
Electric Field ◽  
Hysteresis Loop ◽  
Ferroelectric Properties ◽  
Electric Displacement ◽  
Hysteresis Loops ◽  
Ferroelectric Ceramics ◽  
Domain Growth ◽  
Thermodynamic Approach ◽  
Hysteresis Model ◽  
Self Consistent

Most key elements of ferroelectric properties are defined through the hysteresis loops. For a ferroelectric ceramic, its loop is contributed collectively by its constituent grains, each having its own hysteresis loop when the ceramic polycrystal is under a cyclic electric field. In this paper, we propose a polycrystal hysteresis model so that the hysteresis loop of a ceramic can be calculated from the loops of its constituent grains. In this model a micromechanics-based thermodynamic approach is developed to determine the hysteresis behaviour of the constituent grains, and a self-consistent scheme is introduced to translate these behaviours to the polycrystal level. This theory differs from the classical phenomenological ones in that it is a micromechanics-based thermodynamic approach and it can provide the evolution of new domain concentration among the constituent grains. It also differs from some recent micromechanics studies in its secant form of self-consistent formulation and in its application of irreversible thermodynamics to derive the kinetic equation of domain growth. To put this two-level micromechanics theory in perspective, it is applied to a ceramic PLZT 8/65/35, to calculate its hysteresis loop between the electric displacement and the electric field ( D versus E ), and the butterfly-shaped longitudinal strain versus the electric field relation ( ϵ versus E ). The calculated results are found to be in good quantitative agreement with the test data. The corresponding evolution of new domain concentration c 1 and the individual hysteresis loops of several selected grains—along with those of the overall polycrystal—are also illustrated.

Vortices evolution in ideal (M)HD

2021 ◽  
Author(s):  
José Roberto Canivete Cuissa ◽  
Oskar Steiner
Keyword(s):  
Evolution Equation ◽  
Solar Atmosphere ◽  
Vortex Dynamics ◽  
Shear Flows ◽  
Dynamical Equation ◽  
Space Plasma ◽  
Optimal Criterion ◽  
Swirling Strength ◽  
Vortex Tubes

<p>Vortices and vortex tubes are ubiquitous in the solar atmosphere and space plasma. In order to identify vortices and to study their evolution, we seek a suitable mathematical criterium for which a dynamical equation exists. So far, the only option available is given by the vorticity, which however is not the optimal criterion since it can be biased by shear flows. Therefore, we look at another criterion, the swirling strength, for which we found an evolution equation, which we suggest as a novel tool for the analysis of vortex dynamics in (magneto-)hydrodynamics. We highlight a few results obtained by applying the swirling strength and its dynamical equation to simulations of the solar atmosphere.</p>

Local Field Effects Near Surfaces of Small Systems

1994 ◽  
Vol 366 ◽  
Author(s):  
David Beaglehole
Keyword(s):  
Dielectric Constant ◽  
External Field ◽  
Electric Field ◽  
Local Field ◽  
Computer Calculation ◽  
Local Fields ◽  
Small Systems ◽  
Shape Dependence ◽  
Self Consistent ◽  
Reflection Of Light

ABSTRACTThe interaction of light with a system of molecules depends upon the polarisation induced by an external electric field, which depends not only upon the external field but also upon the local fields due to neighboring polarised molecules. These local fields result in the traditional Clausius-Mossotti (CM) dielectric constant for a molecule deeply imbedded in a medium. Near the surface the local fields are altered, and the dielectric constant becomes anisotropic and dependent upon depth into the medium. The local fields are shape dependent in small systems and differ substantially from the CM value.A self-consistent computer calculation of the local fields has been implemented, and these effects will be shown using molecule positions and polarisabilities typical of liquids and crystals. The shape dependence of small systems, the reflection of light from liquids with fluctuating surfaces, and the effect of supporting substrates will be described.

scholarly journals Direct simulation on nonlinear thermokinetic phenomena due to induced-charge electroosmosis

2018 ◽  
Vol 855 ◽  
pp. 736-769 ◽  
Author(s):  
Hideyuki Sugioka
Keyword(s):  
Electric Field ◽  
Vortex Flow ◽  
Direct Simulation ◽  
General Phenomenon ◽  
Dielectric Particles ◽  
Self Consistent ◽  
Physics Simulation ◽  
Normal Diffusion ◽  
Consistent Manner ◽  
The Stokes Equation

Previously, we proposed a novel mechanism to produce a nonlinear thermokinetic phenomenon (NTKP) around a metal cylinder in an electrolyte on the basis of analytical discussion. In this study, by using a non-steady direct multi-physics simulation technique based on the Stokes equation coupled with the electroosmotic equation that considers normal diffusion, electrophoresis and thermal diffusion, we directly verify the NTKP and show that the original driving force is the excess ions pressed on the particle by the thermokinetic force and that the NTKP vortex flow around the particle is generated by the interaction between the excess ion and the electric field that is made by the excess ions and/or the Seebeck electric field due to the blocking boundary condition on the wall. Namely, two types of NTKP exist and they are explained in a self-consistent manner by our new theory. In addition, through the discussion of a dielectric particle, we show that the NTKP is a general phenomenon that can be found in both metal and dielectric particles. We believe that our findings provide a new unified viewpoint to understand complex thermokinetic phenomena near metal and dielectric particles.

Electric Field Gradient Calculations of Various Borides

1996 ◽  
Vol 51 (5-6) ◽  
pp. 527-533 ◽  
Author(s):  
K. Schwarz ◽  
H. Ripplinger ◽  
P. Blaha
Keyword(s):  
Electric Field ◽  
First Principles ◽  
Density Functional ◽  
The Self ◽  
Full Potential ◽  
Electric Field Gradients ◽  
Charge Density Distribution ◽  
Functional Theory ◽  
Field Gradients ◽  
Self Consistent

Abstract A first-principles method for the computation of electric field gradients (EFG) is illustrated for various borides. It is based on energy band calculations using the full-potential linearized aug-mented plane wave (LAPW) method within density functional theory. From the self-consistent charge density distribution the EFG is obtained without further approximations by numerically solving Poisson's equation. The dependence of the EFG on structure, chemical composition or substitution is demonstrated for the diborides MB2 (with M = Ti, V, Cr, Zr, Nb, Mo, and Ta), the hexaborides (CaB6, SrB6 and BaB6) and boron carbide which is closely related to α-boron.

Sign in / Sign up

Export Citation Format

Share Document