Magnetic field driven micro-convection in the Hele-Shaw cell: the Brinkman model and its comparison with experiment

2015 ◽  
Vol 774 ◽  
pp. 170-191 ◽  
Author(s):  
G. Kitenbergs ◽  
A. Tatulcenkovs ◽  
K. Ērglis ◽  
O. Petrichenko ◽  
R. Perzynski ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Diffusion Coefficient ◽  
Quantitative Agreement ◽  
Threshold Field ◽  
Brinkman Model ◽  
Diffusion Front ◽  
Darcy Model ◽  
Comparison With Experiment ◽  
Ponderomotive Forces ◽  
Individual Particles

The micro-convection caused by the ponderomotive forces of the self-magnetic field in a magnetic fluid is studied here both numerically and experimentally. The theoretical approach based on the general Brinkman model substantially improves the description with respect to the previously proposed Darcy model. The predictions of both models are here compared to finely controlled experiments. The Brinkman model, in contrast to the Darcy model, allows us to describe the formation of mushrooms on the plumes of the micro-convective flow and the width of the fingers. In the Brinkman approach, excellent quantitative agreement is also obtained for the finger velocity dynamics and the velocity maximal values as a function of the magnetic Rayleigh number. The diffusion coefficient of particles of the water-based magnetic colloid determined by the threshold field strength value of the micro-convection is significantly larger than the diffusion coefficient of individual particles. This result is confirmed by independent measurements of the diffusion coefficient at the smearing of the diffusion front.

COLLECTIVE FIELD THEORY TO MAGNETIC-FIELD-INDUCED SPIN-DENSITY-WAVE-STATE IN BECHGAARD SALTS, (TMTSF)2X

1993 ◽  
Vol 07 (19) ◽  
pp. 3415-3421 ◽  
Author(s):  
ALEXANDRE S. ROZHAVSKY
Keyword(s):  
Magnetic Field ◽  
Spin Density ◽  
Chemical Potential ◽  
Density Wave ◽  
Spin Density Wave ◽  
Hall Conductivity ◽  
Chiral Anomaly ◽  
Threshold Field ◽  
Wave State ◽  
Extended States

A field description of spin-density-wave (SDW) in a quasi-two-dimensional metal with open Fermi surface in magnetic field, is proposed. The SDW transition temperature, T c (H), and the Hall conductivity σxy, are calculated. The dependence T c (H) is found to be different from that of the Bardeen-Cooper-Schrieffer model, in particular, a threshold field, H c , found its natural explanation. It is proved that the quantized Hall conductivity arises from the chiral anomaly terms in the effective action provided there is pinning of chemical potential in the gap of extended states.

Nanofluid Treatment in Existence of Magnetic Field Using Non-Darcy Model for Porous Media

2018 ◽  
pp. 456-555
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Finite Element Method ◽  
Porous Media ◽  
Control Volume ◽  
Convection Heat Transfer ◽  
Darcy Number ◽  
Convection Heat ◽  
Darcy Model ◽  
Flow And Heat Transfer

In this chapter, the non-Darcy model is employed for porous media filled with nanofluid. Both natural and forced convection heat transfer can be analyzed with this model. The governing equations in forms of vorticity stream function are derived and then they are solved via control volume-based finite element method (CVFEM). The effect of Darcy number on nanofluid flow and heat transfer is examined.

Influence of Electric Field and Temperature on Magnetic Field Induced Prolonged Changes of Electric Parameters of Silicon Systems

1995 ◽  
Vol 378 ◽  
Author(s):  
Vladimir M Maslovsky
Keyword(s):  
Magnetic Field ◽  
Diffusion Coefficient ◽  
Electric Field ◽  
Diffusion Activation Energy ◽  
Influence Of Temperature On ◽  
Electric Parameters ◽  
Generation Lifetime ◽  
Equilibrium Defects ◽  
First Time ◽  
Diffusion Activation

AbstractMagnetic field induced prolonged changes (MFIPC) of electric parameters of semiconductor systems is the phenomenon that has been recently established experimentally. In this work it is investigated for the first time the influence of electric field and temperature on duration of MFIPC of carrier generation lifetime in Si subsurface region and the influence of temperature on MFIPC of the MOS structure leakage voltage. The value of determined mobility of generated defects corresponds to the diffusion coefficient of vacancy -impurity complexes. These investigations of MFIPC of microstructure confirm that non-equilibrium defects reactions are limited by diffusion (in the absence of external electric field). It is shown that the corresponding diffusion coefficient is about 10−13 cm2s−1 and the magnitude of diffusion activation energy determined from these investigations is in the range 0.45–0.5 eV. This value is nearly the same as the diffusion coefficient of vacancy-impurity complex.

Perpendicular Magnetic Anisotropy in Fe–N Thin Films: Threshold Field for Irreversible Magnetic Stripe Domain Rotation

SPIN ◽  
2016 ◽  
Vol 06 (04) ◽  
pp. 1640014 ◽  
Author(s):  
L.-C. Garnier ◽  
M. Eddrief ◽  
S. Fin ◽  
D. Bisero ◽  
F. Fortuna ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Film ◽  
Magnetic Anisotropy ◽  
Magnetic Measurements ◽  
Perpendicular Magnetic Anisotropy ◽  
The Body ◽  
Threshold Field ◽  
Iron Nitride ◽  
Magnetic Field Direction ◽  
Stripe Domain

The magnetic properties of an iron nitride thin film obtained by ion implantation have been investigated. N[Formula: see text] ions were implanted in a pristine iron layer epitaxially grown on ZnSe/GaAs(001). X-ray diffraction measurements revealed the formation of body-centered tetragonal N-martensite whose [Formula: see text]-axis is perpendicular to the thin film plane and [Formula: see text]-parameter is close to that of [Formula: see text]-Fe8N. Magnetic measurements disclosed a weak perpendicular magnetic anisotropy (PMA) whose energy density [Formula: see text] was assessed to about 105[Formula: see text]J/m3. A sharp decline of the in-plane magnetocrystalline anisotropy (MCA) was also observed, in comparison with the body-centered cubic iron. The origin of the PMA is attributed to the MCA of N-martensite and/or stress-induced anisotropy. As a result of the PMA, weak magnetic stripe domains with a period of about 130[Formula: see text]nm aligned along the last saturating magnetic field direction were observed at remanence by magnetic force microscopy. The application of an increasing in-plane magnetic field transverse to the stripes [Formula: see text] highlighted a threshold value ([Formula: see text][Formula: see text]T) above which these magnetic domains irreversibly rotated. Interestingly, below this threshold, the stripes do not rotate, leading to a zero remanent magnetization along the direction of the applied field. The interest of this system for magnetization dynamics is discussed.

scholarly journals Diffusion Coefficient in Silicon Solar Cell with Applied Magnetic Field and under Frequency: Electric Equivalent Circuits

2014 ◽  
Vol 04 (02) ◽  
pp. 84-92 ◽  
Author(s):  
Amadou Diao ◽  
Ndeye Thiam ◽  
Martial Zoungrana ◽  
Gokhan Sahin ◽  
Mor Ndiaye ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Diffusion Coefficient ◽  
Solar Cell ◽  
Applied Magnetic Field ◽  
Silicon Solar Cell ◽  
Equivalent Circuits

scholarly journals Influence of Temperature and Frequency on Minority Carrier Diffusion Coefficient in a Silicon Solar Cell under Magnetic Field

2019 ◽  
Vol 11 (10) ◽  
pp. 355-361
Author(s):  
Seydina Diouf ◽  
Mor Ndiaye ◽  
Ndeye Thiam ◽  
Youssou Traore ◽  
Mamadou Lamine Ba ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Diffusion Coefficient ◽  
Solar Cell ◽  
Silicon Solar Cell ◽  
Minority Carrier ◽  
Carrier Diffusion ◽  
Influence Of Temperature

scholarly journals An Investigation of r.f. Travelling Wave Current Drive Using the Model

1988 ◽  
Vol 41 (4) ◽  
pp. 587 ◽  
Author(s):  
WK Bertram
Keyword(s):  
Magnetic Field ◽  
Quantitative Agreement ◽  
Travelling Wave ◽  
Current Drive ◽  
Experimental Investigations ◽  
Initial Increase ◽  
Toroidal Plasma ◽  
Subsequent Decrease ◽  
Observed Behaviour ◽  
Drive Model

Previous experimental investigations into the use of travelling r.f. waves to drive steady toroidal currents in a toroidal plasma have shown that It, the amount of current driven, is strongly dependent on the ratio of the static toroidal magnetic field Bz, to the strength of the r.f. magnetic field BO). This dependence is characterised by an initial increase and subsequent decrease of It when Btl BfIJ increases. It is shown that this observed behaviour is entirely consistent with the behaviour predicted by the <i X B) current drive model. Results from .numerical computations using the <i X B) model show good quantitative agreement with the published experimental results.

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