Observation of soft glassy behavior in a magnetic colloid exposed to an external magnetic field

Soft Matter ◽  
2020 ◽  
Vol 16 (30) ◽  
pp. 7126-7136
Author(s):  
Sithara Vinod ◽  
Philip J. Camp ◽  
John Philip
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Applied Field ◽  
Uniform Magnetic Field ◽  
Volume Fraction ◽  
High Rate ◽  
Glassy Behavior ◽  
Low Volume

Microstructures (viewed in a direction perpendicular and parallel to the applied field) responsible for soft glassy behavior in a ferrofluid of low volume fraction when a uniform magnetic field is applied at a sufficiently high rate.

MHD natural convection of Cu/H2O nanofluid in a horizontal semi-cylinder with a local triangular heater

2018 ◽  
Vol 28 (12) ◽  
pp. 2979-2996 ◽  
Author(s):  
A.S. Dogonchi ◽  
Mikhail A. Sheremet ◽  
Ioan Pop ◽  
D.D. Ganji
Keyword(s):  
Magnetic Field ◽  
Rayleigh Number ◽  
Free Convection ◽  
Shape Factor ◽  
Uniform Magnetic Field ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Horizontal Cylinder ◽  
Content Type ◽  
Nanoparticles Volume Fraction

Purpose The purpose of this study is to investigate free convection of copper-water nanofluid in an upper half of circular horizontal cylinder with a local triangular heater under the effects of uniform magnetic field and cold cylinder shell using control volume finite element method (CVFEM). Design/methodology/approach Governing equations formulated in dimensionless stream function, vorticity and temperature variables using the single-phase nanofluid model with Brinkman correlation for the effective dynamic viscosity and Hamilton and Crosser model for the effective thermal conductivity have been solved numerically by CVFEM. Findings The impacts of control parameters such as the Rayleigh number, Hartmann number, nanoparticles volume fraction, local triangular heater size, shape factor on streamlines and isotherms as well as local and average Nusselt numbers have been examined. The outcomes indicate that the average Nusselt number is an increasing function of the Rayleigh number, shape factor and nanoparticles volume fraction, while it is a decreasing function of the Hartmann number. Originality/value A complete study of the free convection of copper-water nanofluid in an upper half of circular horizontal cylinder with a local triangular heater under the effects of uniform magnetic field and cold cylinder shell using CVFEM is addressed.

Magnetic Field Within a Magnetic Shape Memory Alloy and an Equivalent Uniform Applied Magnetic Field for Model Input

2017 ◽  
Author(s):  
J. Lance Eberle ◽  
Heidi P. Feigenbaum ◽  
Constantin Ciocanel
Keyword(s):  
Magnetic Field ◽  
Shape Memory ◽  
Applied Field ◽  
Volume Fraction ◽  
Unit Cell ◽  
Uniform Field ◽  
Magnetic Shape Memory ◽  
Twin Boundaries ◽  
Short Side ◽  
3 Dimensional

Magnetic shape memory alloys (MSMAs) exhibit recoverable strains of up to 10% due to reorientation of their martensitic tetragonal unit cell. A stress or magnetic field applied to the material will cause the short side of the unit cell (which is approximately aligned with the magnetic easy axis) to align with the input to the material, resulting in an apparent plastic strain. This strain can be fully recovered by an applied stress or magnetic field in a perpendicular direction. When the martensitic variants reorient, twin boundaries, which separate the different variants, form and move throughout the specimen. A number of models have been proposed for MSMAs and many of these models are homogenized, i.e. the models do not account for twin boundaries, but rather account for the volume fraction of material in each variant. These types of models often assume that the MSMA is subject to a uniform field so that there is no appreciable difference in the volume fraction of variants in each location. In this work, we address the issue of how these models can be used when the field is not uniform. In particular, we look at the experiments from Feigenbaum et al., in which a MSMA trained to accommodate three variants, was subject to 3-dimensional magneto-mechanical loading. Due to experimental constraints, the field applied to the MSMA was not uniform. In this work, to understand the actual field distribution during experiments, we performed a high-resolution 3-dimensional finite element analysis (FEA) of the magnetic field experienced by the MSMA sample. The FEA allowed us to determine how non-uniform the experimentally applied field was and the differences between the applied field and the field experienced by the MSMA. Furthermore, we use the FEA to determine the average field experienced by the MSMA, and identify an equivalent uniform applied field that could serve as input for the model. For the latter, we seek a uniform magnetic field which gives similar magnetic field within the MSMA specimen as the true experimental conditions.

IMPORTED CONFORMAL SYMMETRY OF ANYONS IN A UNIFORM MAGNETIC FIELD

1992 ◽  
Vol 06 (08) ◽  
pp. 1229-1242 ◽  
Author(s):  
T. AWAJI ◽  
M. HOTTA
Keyword(s):  
Magnetic Field ◽  
Quantum Mechanics ◽  
External Magnetic Field ◽  
Uniform Magnetic Field ◽  
Conformal Symmetry ◽  
Dynamical Symmetry ◽  
Conformal Group ◽  
Symmetry Consideration

We analyze an N-body quantum mechanics of anyons in an external magnetic field. It is pointed out that an SO(2, 1) dynamical symmetry, which is related to the conformal group, plays an important role in anyon dynamics. It is shown that the two-body spectrum is fully reproduced solely by the symmetry consideration. Moreover, we discuss some constraints on missing states from the symmetry consideration.

Characteristics of Ultrasound Propagation in a Magnetic Fluid Under Uniform Magnetic Field

2003 ◽  
Author(s):  
Masaaki Motozawa ◽  
Tatsuo Sawada
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Fluid ◽  
Uniform Magnetic Field ◽  
Colloidal Particles ◽  
Magnetic Field Intensity ◽  
Magnetic Field Direction ◽  
Ultrasound Propagation ◽  
Ultrasonic Propagation ◽  
The Magnetic Field

When an external magnetic field is applied to a magnetic fluid, some of the colloidal particles coagulate and form chain-like clusters. Properties of ultrasonic propagation wave are changed by these chain-like clusters. We carried out measurement of the ultrasonic propagation velocity in a magnetic fluid. Measurement were made by changing the magnetic field intensity from 0 mT to 570 mT, and the angle between the magnetic field direction and direction of the ultrasound propagation from 0° to 180°. The ultrasound frequencies were 1 MHz, 2 MHz and 4 MHz. Some of experimental results for the characteristics of ultrasound propagation in a magnetic fluid under a uniform magnetic field were reported.

The Wannier Functions of the Lattice Electron in a Uniform Magnetic Field

1966 ◽  
Vol 21 (10) ◽  
pp. 1577-1579 ◽  
Author(s):  
A. Jannussis
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Wave Vector ◽  
Free Electron ◽  
Vector Potential ◽  
Uniform Magnetic Field ◽  
Wannier Function ◽  
Wannier Functions ◽  
Uniform External Magnetic Field

In this paper a generalization of the WANNIER functions is performed for the case of the lattice electron moving in a uniform magnetic field.In the case of the free electron moving in a uniform external magnetic field, the WANNIER function may be obtained directly by the Schrauben-function, if the wave vector k is substituted by the vector potential — (1/c) A (ai).

PDF Evolution of Texture in the Fabrication of Magneto-Active Elastomers

2017 ◽  
Author(s):  
Manuel Aurelio Rodriguez ◽  
Paris von Lockette
Keyword(s):  
Magnetic Field ◽  
External Field ◽  
Potential Energy ◽  
Applied Field ◽  
Magnetic Particles ◽  
Volume Fraction ◽  
Magnetic Potential ◽  
Fabrication Process ◽  
Particle Distributions ◽  
Field Strengths

Magneto-Active elastomers (MAEs) and magneto-rheological elastomers (MREs) are smart materials that consist of hard and soft magnetic particles, respectively, embedded in a flexible matrix. Their actuation capabilities are dependent on the arrangement of particles achieved during the fabrication process. Previous works have shown varying degrees of particle alignment and / or agglomeration as a function of fabrication process variable, most notably volume fraction of the particulates, their magnetic material type (hard vs soft), and the strength of the external field applied during curing. In this work, we simulated the dynamics of magnetic particles suspended in a fluid matrix to predict the evolution of microstructures resulting from these varying process conditions. The simulations accounted for the magnetic interaction of all particles using standard dipole-dipole interaction potentials along with dipole-field potentials developed from the Zeeman Energy. Additionally, the field local to each particle, on which magnetization depends, was determined by the sum of the external fields generated by each member of the ensemble and their demagnetizing fields. Fluid drag forces and short range particle-particle repulsion (non-overlapping) were also considered. These interactions determined the body forces and torques acting on each particle that drove the system of equations of motions for the ensemble of particles. The simulation was carried out over a nearest neighbor periodic unit cell using an adaptive time stepping numerical integration scheme until an equilibrium structure was reached. Structural parameters, related to the magnetic energy, spatial distribution, spatial alignment, and orientation alignments of the particle distributions were defined to characterize the simulated structures. The effect of volume fraction and intensity of the external magnetic field on the achieved particle distributions were studied. At low external field strengths, the particles formed long entangled chains that had very low alignment with the applied field. The remnant magnetic potential energy of these configurations was also significantly low. As the field is increased the length of the chains reduced and the alignment increased. The corresponding change in magnetic potential energy of the system with an increase in the applied field was found to follow a power law fit that spanned a wide range of magnetic field strengths. At low volume fractions the particles aligned rapidly with the field and formed short chains. As the volume fraction of the samples increased the chains grew longer and closer to each other, and magnetic potential of the structure became lower. Results of the simulations suggest that it is possible to tailor the microstructure and thus affect remanent magnetization and magnetization anisotropy, by judicious control of process parameters. This ability could have implications for newly emerging additive manufacturing techniques utilizing suspensions of magnetic particulates.

RADIATIVE DECAY OF A MASSIVE NEUTRINO IN THE WEINBERG–SALAM MODEL WITH MIXING IN A CONSTANT UNIFORM MAGNETIC FIELD

1996 ◽  
Vol 11 (39n40) ◽  
pp. 3119-3126 ◽  
Author(s):  
V. CH. ZHUKOVSKY ◽  
P.A. EMINOV ◽  
A.E. GRIGORUK
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Neutrino Mass ◽  
Uniform Magnetic Field ◽  
Radiative Decay ◽  
Decay Process ◽  
Linearly Polarized ◽  
Free Case ◽  
Neutrino Decay ◽  
Broad Region

Influence of an external magnetic field on the neutrino decay process with emission of a linearly polarized photon is considered. The decay rate is shown to be enhanced as compared to the free case in the broad region where both the nonvanishing neutrino mass and the field make substantial contributions. In the limit of a negligible neutrino mass the emitted photons are totally linearly polarized, which may help in the identification of these photons.

scholarly journals The Statistical Properties of Spin-One DKP Oscillator under an External Magnetic Field in Noncommutative Space

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
S. Hassanabadi ◽  
M. Ghominejad
Keyword(s):  
Magnetic Field ◽  
Thermal Properties ◽  
External Magnetic Field ◽  
Uniform Magnetic Field ◽  
Statistical Properties ◽  
Noncommutative Space

The spin-one Duffin-Kemmer-Petiau oscillator in uniform magnetic field is studied in noncommutative formalism. The corresponding energy is obtained and thereby the corresponding thermal properties are obtained for both commutative and noncommutative cases.

scholarly journals Extensional Magnetorheology of Viscoelastic Human Blood Analogues Loaded with Magnetic Particles

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6930
Author(s):  
João M. Nunes ◽  
Francisco J. Galindo-Rosales ◽  
Laura Campo-Deaño
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Human Blood ◽  
Magnetic Particles ◽  
Volume Fraction ◽  
Flow Direction ◽  
Deborah Number ◽  
Simultaneous Application ◽  
String Structure ◽  
Breakup Time

This study represents a pioneering work on the extensional magnetorheological properties of human blood analogue fluids loaded with magnetic microparticles. Dynabeads M-270 particles were dispersed in Newtonian and viscoelastic blood analogue fluids at 5% wt. Capillary breakup experiments were performed, with and without the influence of an external magnetic field aligned with the flow direction. The presence of the particles increased the viscosity of the fluid, and that increment was larger when embedded within a polymeric matrix. The application of an external magnetic field led to an even larger increment of the viscosity of the working fluids, as the formation of small aggregates induced an increment in the effective volume fraction of particles. Regarding the liquid bridge stability, the Newtonian blood analogue fluid remained as a Newtonian liquid exhibiting a pinch-off at the breakup time in any circumstance. However, in the case of the viscoelastic blood analogue fluid, the presence of the particles and the simultaneous application of the magnetic field enhanced the formation of the beads-on-a-string structure, as the Ohnesorge number remained basically unaltered, whereas the time of the experiment increased due to its larger viscosity, which resulted in a decrease in the Deborah Number. This result was confirmed with fluids containing larger concentrations of xanthan gum.

scholarly journals Non-Uniform Magnetic Field Effects on Ferrofluids Film Boiling: A Numerical Study

2020 ◽  
Author(s):  
Rasool Maroofiazar ◽  
Seyyede Fatemeh Haghgoo
Keyword(s):  
Magnetic Field ◽  
Base Fluid ◽  
Uniform Magnetic Field ◽  
Volume Fraction ◽  
Numerical Study ◽  
Film Boiling ◽  
Vapor Film ◽  
Magnetic Field Effects ◽  
Nanoparticles Volume Fraction ◽  
Film Characteristics

In this paper the effect of magnetic field on film boiling of ferrofluids on a horizontal flat plate has been investigated. The obtained results indicate that adding nanoparticles into the base fluid changes vapor film characteristics mainly due to changes in thermophysical properties of the base fluid. Also, ferrofluids enhances film boiling heat transfer on horizontal plate specially at higher volume concentration of nanoparticles. Another important result of this study is the effect of non-uniform magnetic field on horizontal film boiling characteristics. Application of magnetic field changes vapor film behavior mostly at higher values of magnetic field intensity (400) and nanoparticles volume fraction (4 percent).

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