Temperature-dependent dynamic property of magnetorheological gel composite: experiment and modelling

2021 ◽  
Author(s):  
Runsong Mao ◽  
Guang Zhang ◽  
huixing wang ◽  
Jiong Wang
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Storage Modulus ◽  
Magnetic Field Strength ◽  
Dynamic Property ◽  
Smart Materials ◽  
Effect Of Temperature ◽  
Temperature Dependency ◽  
Temperature Dependent ◽  
Field Strengths

Abstract Of all the smart materials that could vary with the change of external excitations, magnetorheological gel (MRG) is one of the most preeminent composites which appear controllable and reversible responses according to the magnitude of external magnetic field. Temperature is identified as another important driver of the alteration of dynamic property of MRG, which so far has not been studied systematically. The temperature-dependent dynamic property of MRG under different magnetic field strengths are investigated by three kinds of experiments –– strain amplitude, frequency and magnetic field sweep test. The experimental results demonstrate that the storage and loss moduli of MRG display a temperature-induced stiffening effect with a magnetic field, while a temperature-induced softening effect without a magnetic field. Besides, storage modulus improves with magnetic field strength, whereas loss modulus firstly appears a rapid growth and then a gradual reduction with the increment of magnetic field strength. This temperature-dependency of dynamic property is also interpreted through different mechanisms related to the transformation of microstructures of MRG. Furthermore, a modified magnetic dipole model which could predict the relationship between storage modulus and magnetic field strength, combines with the classical Arrhenius equation expressing the effect of temperature on viscosity, to describe the temperature-dependency of storage modulus of MRG under different magnetic field strengths. This paper may provide some useful guidance for designing an MR device.

scholarly journals Investigation of the cosmic ray population and magnetic field strength in the halo of NGC 891

2018 ◽  
Vol 615 ◽  
pp. A98 ◽  
Author(s):  
D. D. Mulcahy ◽  
A. Horneffer ◽  
R. Beck ◽  
M. Krause ◽  
P. Schmidt ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Low Frequency ◽  
Cosmic Ray ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Low Frequencies ◽  
Very Large Array ◽  
Field Strengths

Context. Cosmic rays and magnetic fields play an important role for the formation and dynamics of gaseous halos of galaxies. Aims. Low-frequency radio continuum observations of edge-on galaxies are ideal to study cosmic-ray electrons (CREs) in halos via radio synchrotron emission and to measure magnetic field strengths. Spectral information can be used to test models of CRE propagation. Free–free absorption by ionized gas at low frequencies allows us to investigate the properties of the warm ionized medium in the disk. Methods. We obtained new observations of the edge-on spiral galaxy NGC 891 at 129–163 MHz with the LOw Frequency ARray (LOFAR) and at 13–18 GHz with the Arcminute Microkelvin Imager (AMI) and combine them with recent high-resolution Very Large Array (VLA) observations at 1–2 GHz, enabling us to study the radio continuum emission over two orders of magnitude in frequency. Results. The spectrum of the integrated nonthermal flux density can be fitted by a power law with a spectral steepening towards higher frequencies or by a curved polynomial. Spectral flattening at low frequencies due to free–free absorption is detected in star-forming regions of the disk. The mean magnetic field strength in the halo is 7 ± 2 μG. The scale heights of the nonthermal halo emission at 146 MHz are larger than those at 1.5 GHz everywhere, with a mean ratio of 1.7 ± 0.3, indicating that spectral ageing of CREs is important and that diffusive propagation dominates. The halo scale heights at 146 MHz decrease with increasing magnetic field strengths which is a signature of dominating synchrotron losses of CREs. On the other hand, the spectral index between 146 MHz and 1.5 GHz linearly steepens from the disk to the halo, indicating that advection rather than diffusion is the dominating CRE transport process. This issue calls for refined modelling of CRE propagation. Conclusions. Free–free absorption is probably important at and below about 150 MHz in the disks of edge-on galaxies. To reliably separate the thermal and nonthermal emission components, to investigate spectral steepening due to CRE energy losses, and to measure magnetic field strengths in the disk and halo, wide frequency coverage and high spatial resolution are indispensable.

scholarly journals Programmable shunt valve interactions with osseointegrated hearing devices

2017 ◽  
Vol 19 (4) ◽  
pp. 384-390
Author(s):  
Matthew J. Pierson ◽  
Daniel Wehrmann ◽  
J. Andrew Albers ◽  
Najib E. El Tecle ◽  
Dary Costa ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Shunt Valve ◽  
Vp Shunt ◽  
Magnetic Attachment ◽  
Hearing Devices ◽  
Programmable Valves ◽  
The Magnetic Field ◽  
Field Strengths

OBJECTIVE Patients with ventriculoperitoneal (VP) shunts with programmable valves who would benefit from osseointegrated hearing devices (OIHDs) represent a unique population. The aim of this study was to evaluate the magnetic field strengths of 4 OIHDs and their interactions with 5 programmable VP shunt valves. METHODS Magnetic field strength was measured as a function of distance for each hearing device (Cochlear Baha 5, Cochlear Baha BP110, Oticon Ponto Plus Power, and Medtronic Sophono) in the following modes: inactive, active in quiet, and active in 60 decibels of background noise in the sound booth. The hearing devices were introduced to each shunt valve (Aesculap proGAV, Aesculap proGAV 2.0, Codman Hakim, Codman Certas, and Medtronic Strata II) also as a function of distance in these identical 3 settings. Each trial was repeated 5 times. Between each trial, the valves were assessed for a change in setting. Finally, using a skull model, the devices were introduced to each other in standard anatomical locations and the valves were assessed for a change in settings. RESULTS The maximum magnetic field strengths generated by the Cochlear Baha 5, BP110, and Oticon OIHDs were 1.1, 36.2, and 48.7 gauss (G), respectively. The maximum strength generated by the Sophono device was > 800 G. The magnetic field strength of the hearing devices decreased markedly with increasing distance from the device. The strength of the Sophono's magnetic attachment decreased to 34.8 G at 5 mm. The Codman Hakim, Codman Certas, and Medtronic Strata II valve settings changed when rotating the valves next to the Sophono abutment. No other changes in valve settings occurred in the distance or anatomical models for any other trials. CONCLUSIONS This is the first study evaluating the interaction between OIHDs and programmable VP shunt valves. The findings suggest that it is safe to use these devices together without having to switch to a nonprogrammable valve or move the shunt valve to a more distant location. Still, care should be taken if the Sophono device is used to ensure that the valve is ≥ 5 mm away from the magnetic attachment.

scholarly journals Effect of magnetic field strength on the linewidth and spin-lattice relaxation time of the thiocyanate carbon of cyanylated β-lactoglobulin B: optimization of the experimental parameters for observing thiocyanate carbons in proteins

1995 ◽  
Vol 306 (2) ◽  
pp. 531-535
Author(s):  
J P G Malthouse ◽  
P Phelan
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Chemical Shift Anisotropy ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Field Strengths

The linewidths and spin-lattice relaxation times of the 13C-n.m.r. signal at 109.7 p.p.m. due to the thiocyanate carbon of intact [cyanato-13C]cyanylated-beta-lactoglobulin-B have been determined at magnetic field strengths of 1.88, 6.34 and 11.74 T as well as the spin-lattice relaxation times of its backbone alpha-carbon atoms. The linewidths were directly proportional to the square of the magnetic field strength and we conclude that, at magnetic field strengths of 6.34 T or above, more than 70% of the linewidth will be determined by chemical-shift anisotropy. We estimate that the spin-lattice relaxation time resulting from the chemical-shift anisotropy of the thiocyanate carbon is 1.52 +/- 0.1 s and we conclude that for magnetic field strengths of 6.34 T and above the observed spin-lattice relaxation time of the thiocyanate carbon will be essentially independent of magnetic field strength. Using the rigid-rotor model we obtain estimates of the rotational correlation time of [cyanato-13C]cyanylated-beta-lactoglobulin-B and of the chemical-shift anisotropy shielding tensor of its thiocyanate carbon. We have calculated the linewidths and spin-lattice relaxation times of thiocyanate carbons at magnetic field strengths of 1.88-14.1 T in proteins with M(r) values in the range 10,000-400,000. The effects of magnetic field strength on the resolution and signal-to-noise ratios of the signals due to thiocyanate carbons attached to proteins of M(r) greater than 10,000 are discussed.

A portable apparatus for measuring the magnetic field strength in an electromagnetic wave

1931 ◽  
Vol 27 (3) ◽  
pp. 481-489
Author(s):  
L. G. Vedy ◽  
A. F. Wilkins
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Wave ◽  
Magnetic Fields ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Special Means ◽  
Portable Apparatus ◽  
The Magnetic Field ◽  
Field Strengths

A portable apparatus is described which is capable of measuring directly, by means of a loop aerial, the magnetic field in an electromagnetic wave. Accurate measurements are possible of magnetic fields corresponding to field strengths of 0·2 millivolts per metre. Special means of providing small known calibrating E. M. F. S are described. The apparatus can be used to measure signals over the range 6 microvolts to 300 millivolts. Used in conjunction with a small portable vertical aerial, field strengths down to 2 microvolts per metre can be measured.

MAGNETORHEOLOGICAL CHARACTERIZATION OF ORGANOCLAY ADDED CARBONYL-IRON SUSPENSIONS

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1142-1148 ◽  
Author(s):  
S. T. LIM ◽  
M. S. CHO ◽  
H. J. CHOI ◽  
M. S. JHON
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Carbonyl Iron ◽  
Flow Behavior ◽  
Steady Shear ◽  
Precise Control ◽  
Additive Particles ◽  
Shear Modes ◽  
Field Strengths

Carbonyl-iron (CI) based magnetorheological (MR) fluid containing submicron-sized additive particles was prepared. The flow behavior at steady and oscillatory shear modes was investigated by comparing flow properties of CI-mineral oil suspensions without an additive via precise control of magnetic field strength. To enhance the dispersion stability and to examine submicron-sized filler effect for the CI suspensions, organically modified montmorillonite (organoclay) was added to the CI suspensions. In addition, with the precision control of magnetic field strength, we examined the novel features of submicron-sized particle filled CI suspensions, especially under weak magnetic field strengths, in steady shear modes; a temporal decrease of steady shear viscosity in sweeping magnetic field strengths was observed.

scholarly journals Physics of Thermonuclear Explosions: Magnetic Field Effects on Deflagration Fronts and Observable Consequences

2021 ◽  
Vol 923 (2) ◽  
pp. 210
Author(s):  
Boyan Hristov ◽  
Peter Hoeflich ◽  
David C. Collins
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Phase 1 ◽  
Hybrid Approach ◽  
Light Curves ◽  
Late Time ◽  
Magnetic Field Effects ◽  
Second Stage ◽  
Field Strengths

Abstract We present a study of the influence of magnetic field strength and morphology in Type Ia supernovae and their late-time light curves and spectra. In order to both capture self-consistent magnetic field topologies and evolve our models to late times, a two-stage approach is taken. We study the early deflagration phase (∼1 s) using a variety of magnetic field strengths and find that the topology of the field is set by the burning, independent of the initial strength. We study late-time (∼1000 days) light curves and spectra with a variety of magnetic field topologies and infer magnetic field strengths from observed supernovae. Lower limits are found to be 106 G. This is determined by the escape, or lack thereof, of positrons that are tied to the magnetic field. The first stage employs 3D MHD and a local burning approximation and uses the code Enzo. The second stage employs a hybrid approach, with 3D radiation and positron transport and spherical hydrodynamics. The second stage uses the code HYDRA. In our models, magnetic field amplification remains small during the early deflagration phase. Late-time spectra bear the imprint of both magnetic field strength and morphology. Implications for alternative explosion scenarios are discussed.

scholarly journals Recent Progress in Isotropic Magnetorheological Elastomers and Their Properties: A Review

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3023
Author(s):  
Muhammad Arslan Hafeez ◽  
Muhammad Usman ◽  
Malik Adeel Umer ◽  
Asad Hanif
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Smart Materials ◽  
Recent Progress ◽  
Volume Fraction ◽  
Shear Loading ◽  
Wide Field ◽  
Magnetorheological Elastomers ◽  
Filler Particles

Magnetorheological elastomers (MREs) are magneto-sensitive smart materials, widely used in various applications, i.e., construction, automotive, electrics, electronics, medical, minimally invasive surgery, and robotics. Such a wide field of applications is due to their superior properties, including morphological, dynamic mechanical, magnetorheological, thermal, friction and wear, and complex torsional properties. The objective of this review is to provide a comprehensive review of the recent progress in isotropic MREs, with the main focus on their properties. We first present the background and introduction of the isotropic MREs. Then, the preparation of filler particles, fabrication methods of isotropic MREs, and key parameters of the fabrication process—including types of polymer matrices and filler particles, filler particles size and volume fraction, additives, curing time/temperature, and magnetic field strength—are discussed in a separate section. Additionally, the properties of various isotropic MREs, under specific magnetic field strength and tensile, compressive, or shear loading conditions, are reviewed in detail. The current review concludes with a summary of the properties of isotropic MREs, highlights unexplored research areas in isotropic MREs, and provides an outlook of the future opportunities of this innovative field.

scholarly journals Fluctuations of the magnetic-field strength of sunspots within one day

1968 ◽  
Vol 35 ◽  
pp. 214-214
Author(s):  
H. Künzel
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
General Tendency ◽  
Mean Error ◽  
The Mean ◽  
Short Time ◽  
The Magnetic Field ◽  
Field Strengths

In the period of May-June 1965, the magnetic-field strengths of twenty sunspots were measured in order to investigate fluctuations within one day. The results of spectrograms, which were taken in the interval of one hour, are given in graphs. The mean error of one value has the size of ± 169 gauss. The graphs show the general tendency in the behaviour of field strength. Fluctuations of magnetic-field strength up to 800 gauss within a few hours were found. The short-time fluctuations shown in the graphs are mostly smaller than the mean error and therefore probably not real.For more details see Astron. Nachr., 289 (1967), 233.

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