Instability of a plane conducting free surface submitted to an alternating magnetic field

This paper considers the stability of a horizontal liquid-metal free surface in the presence of a horizontal alternating magnetic field. A weak formulation is used to derive a generalized Mathieu–Hill equation for the evolution of surface perturbations. Previous studies which rely on time-averaging the electromagnetic force over one field cycle have predicted a generally weak instability, but we find much larger growth rates near the resonances, where the surface wave frequency is an integral multiple of the field frequency. The method can be extended to include viscous and ohmic damping; the former has little effect, while the latter damps all waves except those whose frequency is close to the field frequency. Growth rates can be closely approximated by simple algebraic formulae, as can the critical magnetic field strength for the onset of instability.

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Liquid Metal Free Surface Motion Submerged in an AC Magnetic Field

Materials Science Forum ◽

10.4028/www.scientific.net/msf.561-565.1071 ◽

2007 ◽

Vol 561-565 ◽

pp. 1071-1074

Author(s):

Kazuhiko Iwai ◽

Shigeo Asai

Keyword(s):

Magnetic Field ◽

Free Surface ◽

Liquid Metal ◽

Standing Wave ◽

Skin Layer ◽

Alternating Magnetic Field ◽

Liquid Gallium ◽

Field Frequency ◽

Surface Motion ◽

The Magnetic Field

Free surface motion of a liquid metal submerged in an alternating magnetic field has been examined. A copper vessel filled with a liquid gallium is set in a coil for the imposition of the alternating magnetic field. The alternating magnetic field penetrates into a liquid gallium only from an upper free surface because thickness of the copper vessel is larger than the electromagnetic skin layer of copper. Time variation of displacement of the standing wave loop excited on the free surface is detected by a laser level sensor. The standing wave was suppressed not only by intensification of the magnetic field magnitude but also increase of the magnetic field frequency.

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114 Selected Oscillation Modes Observed at the Free Surface of Magnet-Magnetic Fluid System Subjected to Alternating Magnetic Field

The Proceedings of Conference of Tohoku Branch ◽

10.1299/jsmeth.2014.49.29 ◽

2014 ◽

Vol 2014.49 (0) ◽

pp. 29-30

Author(s):

Masahide ITO ◽

Seiichi SUDO ◽

Hideya NISHIYAMA

Keyword(s):

Magnetic Field ◽

Free Surface ◽

Magnetic Fluid ◽

Alternating Magnetic Field ◽

Fluid System ◽

Oscillation Modes

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MHD instabilities of a cylindrical plasma with a realistic energy equation

Journal of Plasma Physics ◽

10.1017/s0022377800012095 ◽

1987 ◽

Vol 37 (2) ◽

pp. 175-184 ◽

Cited By ~ 1

Author(s):

Guidetta Torricelli-Ciamponi ◽

Vittorio Ciampolini ◽

Claudio Chiuderi

Keyword(s):

Magnetic Field ◽

Time Scales ◽

Growth Rates ◽

Thermal Conduction ◽

Energy Equation ◽

Magnetized Plasma ◽

Line Radiation ◽

Mhd Instabilities ◽

Solar Plasmas ◽

The Stability

The influence of a realistic energy equation on the stability of a cylindrical magnetized plasma in a force-free magnetic field is discussed. Thermal conduction, heating and line radiation are included in the treatment. Explicit growth rates for the m = 0 and m = 1 modes are derived and compared with the standard adiabatic or incompressible time-scales. Finally, the relevance of these results for laboratory and solar plasmas is discussed.

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Experimental Evaluation on the Heating Efficiency of Magnetoferritin Nanoparticles in an Alternating Magnetic Field

Nanomaterials ◽

10.3390/nano9101457 ◽

2019 ◽

Vol 9 (10) ◽

pp. 1457 ◽

Cited By ~ 3

Author(s):

Huangtao Xu ◽

Yongxin Pan

Keyword(s):

Magnetic Field ◽

Relaxation Time ◽

Magnetic Hyperthermia ◽

Alternating Magnetic Field ◽

Core Size ◽

Hyperthermia Treatment ◽

Field Frequency ◽

Glycerol Water ◽

Heating Efficiency ◽

Néel Relaxation

The superparamagnetic substance magnetoferritin is a potential bio-nanomaterial for tumor magnetic hyperthermia because of its active tumor-targeting outer protein shell, uniform and tunable nanosized inner mineral core, monodispersity and good biocompatibility. Here, we evaluated the heating efficiency of magnetoferritin nanoparticles in an alternating magnetic field (AMF). The effects of core-size, Fe concentration, viscosity, and field frequency and amplitude were investigated. Under 805.5 kHz and 19.5 kA/m, temperature rise (ΔT) and specific loss power (SLP) measured on magnetoferritin nanoparticles with core size of 4.8 nm at 5 mg/mL were 14.2 °C (at 6 min) and 68.6 W/g, respectively. The SLP increased with core-size, Fe concentration, AMF frequency, and amplitude. Given that: (1) the SLP was insensitive to viscosity of glycerol-water solutions and (2) both the calculated effective relaxation time and the fitted relaxation time were closer to Néel relaxation time, we propose that the heating generation mechanism of magnetoferritin nanoparticles is dominated by the Néel relaxation. This work provides new insights into the heating efficiency of magnetoferritin and potential future applications for tumor magnetic hyperthermia treatment and heat-triggered drug release.

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Resistive instability in a uniformly rotating magnetoplasma

Journal of Plasma Physics ◽

10.1017/s0022377800025691 ◽

1971 ◽

Vol 6 (1) ◽

pp. 73-85

Author(s):

A. D. Lunn

Keyword(s):

Magnetic Field ◽

Growth Rates ◽

Larmor Radius ◽

Closed Set ◽

Finite Larmor Radius ◽

Integral Methods ◽

Stabilizing Effect ◽

Instability Growth ◽

Linear Differential ◽

The Stability

A closed set of guiding centre equations, derived for a rotating plasma in a static magnetic field, is applied to the problem of the stability of a plasma in a sheared field. The rotation is found to have a stabilizing effect in the absence of resistivity.A pair of coupled, linear differential equations is derived for the rotating plasma in a weakly sheared field. Dispersion relations are obtained by phase integral methods and, in the absence of finite Larmor radius effects and rotation, instability growth rates proportional to η½13 are found which become proportional to when either is included. The inclusion of both finite Larmor radius and rotation gives growing instabilities proportional to η which are stabilized by the rotation when the finite Larmor radius terms predominate.

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Linear stability of thermocapillary convection in cylindrical liquid bridges under axial magnetic fields

Journal of Fluid Mechanics ◽

10.1017/s0022112099005698 ◽

1999 ◽

Vol 394 ◽

pp. 281-302 ◽

Cited By ~ 26

Author(s):

M. PRANGE ◽

M. WANSCHURA ◽

H. C. KUHLMANN ◽

H. J. RATH

Keyword(s):

Magnetic Field ◽

Free Surface ◽

Magnetic Fields ◽

Prandtl Number ◽

Linear Stability ◽

Thermocapillary Convection ◽

Axial Magnetic Field ◽

Unstable Mode ◽

Linear Stability Theory ◽

The Stability

The stability of axisymmetric steady thermocapillary convection of electrically conducting fluids in half-zones under the influence of a static axial magnetic field is investigated numerically by linear stability theory. In addition, the energy transfer between the basic state and a disturbance is considered in order to elucidate the mechanics of the most unstable mode. Axial magnetic fields cause a concentration of the thermocapillary flow near the free surface of the liquid bridge. For the low Prandtl number fluids considered, the most dangerous disturbance is a non-axisymmetric steady mode. It is found that axial magnetic fields act to stabilize the basic state. The stabilizing effect increases with the Prandtl number and decreases with the zone height, the heat transfer rate at the free surface and buoyancy when the heating is from below. The magnetic field also influences the azimuthal symmetry of the most unstable mode.

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Tumor therapy by fast moving magnetic nanoparticle under low-frequency alternating magnetic field

Journal of Innovative Optical Health Sciences ◽

10.1142/s179354581550008x ◽

2015 ◽

Vol 08 (02) ◽

pp. 1550008 ◽

Cited By ~ 2

Author(s):

Yangyang Liu ◽

Zhiyu Qian ◽

Jianhua Yin ◽

Xiao Wang

Keyword(s):

Magnetic Field ◽

Tumor Cells ◽

Magnetic Nanoparticle ◽

Tumor Therapy ◽

Low Frequency ◽

Alternating Magnetic Field ◽

Nanoparticle Concentration ◽

Field Frequency ◽

A New Technique ◽

The Magnetic Field

Magnetic nanoparticle plays an important role in biomedical engineering, especially in tumor therapy. In this paper, a new technique has been developed by using the rapid moving magnetic nanoparticle under a low-frequency alternating magnetic field (LFAMF) to kill tumor cells. The LFAMF system which was used to drive magnetic nanoparticles (MNPs) was setup with the magnetic field frequency and power range at ∼ 10–100 Hz and ∼ 10–200 mT, respectively. During the experiment, the LFAMF was adjusted at different frequencies and power levels. The experimental results show that the liver tumor cells (HepG2) mixed with MNPs (10 μg/mL) became partial fragments when exposed in the LFAMF with different frequencies (∼ 10–100 Hz) and power (∼ 10–200 mT), and the higher the frequency or the power, the more the tumor cells were killed at the same magnetic nanoparticle concentration. Conclusion: Tumor cells were effectively damaged by MNPs under LFAMF, which suggests that they had great potential to be applied in tumor therapy.

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