Electromagneto-Thermoelastic Plane Waves in Solids With Thermal Relaxation

1972 ◽  
Vol 39 (1) ◽  
pp. 108-113 ◽  
Author(s):  
A. H. Nayfeh ◽  
S. Nemat-Nasser
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Thermal Field ◽  
Plane Waves ◽  
Electric Displacement ◽  
Thermal Relaxation ◽  
Displacement Current ◽  
Perturbation Techniques ◽  
Thermoelastic Waves ◽  
The Magnetic Field

Perturbation techniques are used to study the influence of small thermoelastic and magnetoelastic couplings on the propagation of plane electromagneto-thermoelastic waves in an unbounded isotropic medium. The thermal relaxation time of heat conduction, and the electric displacement current are included in the analysis. It is found that the thermal field may affect transverse motions, and that the magnetic field may affect motions that occur parallel to its line of action.

Magneto-thermo-elastic plane waves

1965 ◽  
Vol 61 (4) ◽  
pp. 939-944 ◽  
Author(s):  
C. M. Purushothama
Keyword(s):  
Magnetic Field ◽  
Wave Propagation ◽  
Shear Wave ◽  
Wave Velocity ◽  
Compression Wave ◽  
Thermal Field ◽  
Plane Waves ◽  
Elastic Plane ◽  
Magnetic Diffusivity ◽  
The Magnetic Field

AbstractThe combined effects of uniform thermal and magnetic fields on the propagation of plane waves in a homogeneous, initially unstressed, electrically conducting elastic medium have been investigated.When the magnetic field is parallel to the direction of wave propagation, the compression wave is purely thermo-elastic and the shear wave is purely magneto-elastic in nature. For a transverse magnetic field, the shear waves remain elastic whereas the compression wave assumes magneto-thermo-elastic character due to the coupling of all the three fields—mechanical, magnetic and thermal. In the general case, the waves polarized in the plane of the direction of wave propagation and the magnetic field are not only coupled but are also influenced by the thermal field, once again exhibiting the coupling of the three fields. The shear wave polarized transverse to the plane retains its magneto-elastic character.Notation.Hi = primary magnetic field components,ht = induced magnetic field components,To = initial thermal field,θ = induced thermal field,C = compression wave velocity.S = shear wave velocity,ui = displacement components,cv = specific heat at constant volume,k = thermal conductivity,η = magnetic diffusivity,μe = magnetic permeability,λ, μ = Lamé's constants,β = ratio of coefficient of volume expansion to isothermal compressibility.

emperature Dependence of the Magnetoresistance Effect in Metals

2012 ◽  
Vol 67 (8-9) ◽  
pp. 498-508
Author(s):  
Stanisław Olszewski
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Metal Temperature ◽  
Time Increase ◽  
Electric Conduction ◽  
Magnetoresistance Effect ◽  
Metal Sample ◽  
The Magnetic Field

The paper examines a well-known experimental property of increase of the magnetoresistance effect in a metal observed with a decrease of the metal temperature. This property is explained by the fact that magnetoresistance is a quantity proportional to the relaxation time of the electric conduction of the metal sample which is a parameter observed in the absence of the magnetic field. Since the electric conduction, as well as the corresponding relaxation time, increase with the lowering of temperature, they provide us necessarily with an increase of magnetoresistance. The phenomenon is investigated quantitatively in this paper for numerous metal cases taken as examples.

MAGNETORESISTANCE IN COPPER

2008 ◽  
Vol 22 (25n26) ◽  
pp. 4434-4441
Author(s):  
SHIGEJI FUJITA ◽  
NEBI DEMEZ ◽  
JEONG-HYUK KIM ◽  
H. C. HO
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Kinetic Theory ◽  
Anisotropic Magnetoresistance ◽  
Magnetic Field Direction ◽  
Conduction Electrons ◽  
Fcc Lattice ◽  
A Charge ◽  
The Magnetic Field ◽  
Cyclotron Mass

The motion of the guiding center of magnetic circulation generates a charge transport. By applying kinetic theory to the guiding center motion, an expression for the magnetoconductivity σ is obtained: σ = e2ncτ/M*, where M* is the magnetotransport mass distinct from the cyclotron mass, nc the density of the conduction electrons, and τ the relaxation time. The density nc depends on the magnetic field direction relative to copper's fcc lattice, when Cu's Fermi surface is nonspherical with “necks”. The anisotropic magnetoresistance is analyzed based on a one-parameter model, and compared with experiments. A good fit is obtained.

DEPHASING IN PRESENCE OF A MAGNETIC FIELD

2007 ◽  
Vol 06 (03n04) ◽  
pp. 261-264 ◽  
Author(s):  
A. V. GERMANENKO ◽  
V. A. LARIONOVA ◽  
I. V. GORNYI ◽  
G. M. MINKOV
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Relaxation Rate ◽  
Negative Magnetoresistance ◽  
Phase Relaxation ◽  
Quasi Momentum ◽  
Fitting Procedure ◽  
Electron Interference ◽  
Momentum Relaxation ◽  
The Magnetic Field

Effect of the magnetic field on the rate of phase breaking is studied. It is shown that the magnetic field resulting in the decrease of phase relaxation rate [Formula: see text] makes the negative magnetoresistance due to suppression of the electron interference to be smoother in shape and lower in magnitude than that found with constant [Formula: see text]-value. Nevertheless our analysis shows that experimental magnetoconductance curves can be well fitted by the Hikami–Larkin–Nagaoka expression.1 The fitting procedure gives the value of τ/τϕ, where τ is the quasi-momentum relaxation time, which is close to the value of τ/τϕ(B = 0) with an accuracy of 25% or better when the temperature varies within the range from 0.4 to 10 K. The value of the prefactor α found from this procedure lies within the interval 0.9–1.2.

scholarly journals VII. On the fundamental formulations of electrodynamics

1920 ◽  
Vol 220 (571-581) ◽  
pp. 207-245 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Force ◽  
Electromagnetic Interaction ◽  
Good Deal ◽  
Magnetic Polarity ◽  
Displacement Current ◽  
Linear Induction ◽  
Energy Relations ◽  
The Magnetic Field ◽  
Effective Representation

1. Modern electrical theory based on Maxwell’s concept of an æthereal displacement current, is generally regarded as being sufficiently complete in itself to cover all actions so far revealed to us, if we exclude those intra-atomic phenomena which probably involve some additional but not necessarily inconsistent action in their working. There, still, however exists a good deal of uncertainty as to the actual results of the development of this theory in certain directions, and no account has yet been taken of the great degree of latitude allowed by it in its simplest and most general form. For example, in most presentations of the theory of energy streaming in the electromagnetic field the discussion is given in a way which might lead one to believe that Poynting’s form of the theory is the only one conceivable. A single alternative has on one occasiont been suggested, but rather as an improvement on Poynting’s form than as an indication of its uncertainty. Whilst it cannot be denied that Poynting’s theory is probably the most appropriate one yet formulated, yet it must be recognised that there are an infinite number of fundamentally different forms each of which is itself perfectly consistent with Maxwell’s theory as expressed in his differential equations of electromagnetic interaction. Again, but now we are on a different plane, it has usually been stated that Maxwell’s theory is not of sufficient generality to cover the cases where there exists the complication of non-linear induction in ferromagnetic media. This view appears to have originated with the idea that the magnetic force is the fundamental æthereal vector of the magnetic field, whereas, as a matter of fact, the only consistent view of the energy relations of such a field leads to the conclusion that the magnetic induction is the true æthereal vector, the magnetic force being an auxiliary vector derived in the process of averaging the minute current whirls into their effective representation as a distribution of magnetic polarity.

Multiple-relaxation-time lattice Boltzmann study of the magnetic field effects on natural convection of non-Newtonian fluids

2017 ◽  
Vol 28 (11) ◽  
pp. 1750138 ◽  
Author(s):  
Xuguang Yang ◽  
Lei Wang
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Power Law ◽  
Lattice Boltzmann ◽  
Hartmann Number ◽  
Magnetic Field Effects ◽  
Multiple Relaxation Time ◽  
Number Formula ◽  
Power Law Index ◽  
The Magnetic Field

In this paper, the magnetic field effects on natural convection of power-law non-Newtonian fluids in rectangular enclosures are numerically studied by the multiple-relaxation-time (MRT) lattice Boltzmann method (LBM). To maintain the locality of the LBM, a local computing scheme for shear rate is used. Thus, all simulations can be easily performed on the Graphics Processing Unit (GPU) using NVIDIA’s CUDA, and high computational efficiency can be achieved. The numerical simulations presented here span a wide range of thermal Rayleigh number ([Formula: see text]), Hartmann number ([Formula: see text]), power-law index ([Formula: see text]) and aspect ratio ([Formula: see text]) to identify the different flow patterns and temperature distributions. The results show that the heat transfer rate is increased with the increase of thermal Rayleigh number, while it is decreased with the increase of Hartmann number, and the average Nusselt number is found to decrease with an increase in the power-law index. Moreover, the effects of aspect ratio have also investigated in detail.

Bewegungen der CH3-Gruppen in Methyl-Naphthalin-Kristallen

1972 ◽  
Vol 27 (1) ◽  
pp. 42-50 ◽  
Author(s):  
J. U. Von Schütz ◽  
H. C. Wolf
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Activation Energies ◽  
Rotational Barrier ◽  
Proton Relaxation ◽  
Methyl Groups ◽  
Hindered Rotation ◽  
Proton Relaxation Time ◽  
Methyl Naphthalene ◽  
The Magnetic Field

Abstract The longitudinal proton relaxation time T1 in methyl naphthalene crystals, differing in the arrangement and number of the substituted CH3 groups, was measured as a function of the temperature above 77 °K and the magnetic field between 0.9 and 20 kOe. The results can be described by hindered rotation of the methyl groups with the jumping times and activation energies strongly dependent on the group arrangement. In the β-position the rotational barrier of 0.8 kcal/mol is predominantly determined by the infermolecular interaction, whereas in the case of the a-position and for adjacent CH3’s the hindering potential of 2.4 kcal/mol arises largely from the intramolecular term.

scholarly journals Quantitative Analysis of the Specific Absorption Rate Dependence on the Magnetic Field Strength in ZnxFe3−xO4 Nanoparticles

2020 ◽  
Vol 21 (20) ◽  
pp. 7775
Author(s):  
Mohamed Alae Ait Kerroum ◽  
Cristian Iacovita ◽  
Walid Baaziz ◽  
Dris Ihiawakrim ◽  
Guillaume Rogez ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Large Diameter ◽  
Precipitation Method ◽  
Magnetization Relaxation ◽  
Specific Absorption ◽  
The Magnetic Field ◽  
Néel Relaxation

Superparamagnetic ZnxFe3−xO4 magnetic nanoparticles (0 ≤ x < 0.5) with spherical shapes of 16 nm average diameter and different zinc doping level have been successfully synthesized by co-precipitation method. The homogeneous zinc substitution of iron cations into the magnetite crystalline structure has led to an increase in the saturation magnetization of nanoparticles up to 120 Am2/kg for x ~ 0.3. The specific absorption rate (SAR) values increased considerably when x is varied between 0 and 0.3 and then decreased for x ~ 0.5. The SAR values are reduced upon the immobilization of the nanoparticles in a solid matrix being significantly increased by a pre-alignment step in a uniform static magnetic field before immobilization. The SAR values displayed a quadratic dependence on the alternating magnetic field amplitude (H) up to 35 kA/m. Above this value, a clear saturation effect of SAR was observed that was successfully described qualitatively and quantitatively by considering the non-linear field’s effects and the magnetic field dependence of both Brown and Neel relaxation times. The Neel relaxation time depends more steeply on H as compared with the Brown relaxation time, and the magnetization relaxation might be dominated by the Neel mechanism, even for nanoparticles with large diameter.

scholarly journals ELECTROMAGNETIC-GRAVITATIONAL CONVERSION CROSS-SECTIONS IN EXTERNAL ELECTROMAGNETIC FIELDS

1994 ◽  
Vol 09 (39) ◽  
pp. 3619-3627 ◽  
Author(s):  
HOANG NGOC LONG ◽  
DANG VAN SOA ◽  
TUAN A. TRAN
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Electromagnetic Fields ◽  
Cross Sections ◽  
Differential Cross ◽  
Numerical Evaluation ◽  
Differential Cross Sections ◽  
Perturbation Techniques ◽  
External Electromagnetic Fields ◽  
The Magnetic Field

The classical processes: the conversion of photons into gravitons in the static electromagnetic fields are considered by using Feynman perturbation techniques. The differential cross-sections are presented for the conversion in the electric field of the flat condenser and the magnetic field of the solenoid. A numerical evaluation shows that the cross-sections may have the observable value in the present technical scenario.

Sign in / Sign up

Export Citation Format

Share Document