Regulation Behavior of Microwave Reflectivity in Magnetorheological Fluids

2011 ◽  
Vol 413 ◽  
pp. 213-216
Author(s):  
Ji Jun Fan ◽  
Nan Hui Yu
Keyword(s):  
Magnetic Field ◽  
Experimental Study ◽  
External Magnetic Field ◽  
Field Strength ◽  
Internal Structure ◽  
Magnetic Field Strength ◽  
Particle Concentration ◽  
Microwave Frequency ◽  
Microwave Reflection ◽  
The Given

In this paper, experimental study of the microwave reflection behavior in MRF was carried out. The results showed that at the same frequency the microwave reflectivity of MRF decreased with the increasing of magnetic field strength; and with the increasing of particle concentration, microwave reflectivity decreased, monotonously. Under the given magnetic field, with the increasing of microwave frequency, it first decreased, there is a lowest point at 9.2GHz, and then it increased. Usually, it is considered that the change of internal structure of MRF under external magnetic field is the main reason for the regulation behavior of microwave reflectivity.

Study of Microwave Reflection Behaviour in Fe3O4 Magnetorheological Fluids

2011 ◽  
Vol 287-290 ◽  
pp. 2785-2788
Author(s):  
Nan Hui Yu ◽  
Ji Jun Fan
Keyword(s):  
Magnetic Field ◽  
Experimental Study ◽  
External Magnetic Field ◽  
Field Strength ◽  
Smart Materials ◽  
Particle Concentration ◽  
Critical Concentration ◽  
Microwave Frequency ◽  
Magnetorheological Fluids ◽  
Microwave Reflection

Owing to its unique properties and wide engineering applications, magnetorheological fluids (MRF) has become a hot study area in the field of smart materials. In this paper experimental study of the microwave reflection behavior in MRF was carried out. The results indicated that at the same frequency the microwave reflectivity of MRF decreased with the increasing of magnetic field strength; and with the particle concentration increasing, microwave reflectivity first increased, then decreased, there is a critical concentration of 15%. Under the same magnetic field, with the increasing of microwave frequency, it first decreased, there is a lowest point at 9.2GHz, and then it increased. Usually, it is considered that the change of internal structure of MRF under external magnetic field is the main reason for the regulation behavior of microwave reflectivity.

Experimental Study of a Plasma Produced by a Helical Radio-frequency Structure

1974 ◽  
Vol 52 (22) ◽  
pp. 2246-2249 ◽  
Author(s):  
H. W. H. Van Andel ◽  
M. T. Churchland ◽  
G. Calabrese
Keyword(s):  
Magnetic Field ◽  
Experimental Study ◽  
Field Strength ◽  
Electron Temperature ◽  
Magnetic Field Strength ◽  
Cyclotron Resonance ◽  
Electron Cyclotron Resonance ◽  
Plasma Stability ◽  
Absorption Process ◽  
Moderate Power

A plasma produced by a helical RF structure of the Lisitano type is investigated. Measurements of electron density, electron temperature, and plasma stability are reported as a function of RF frequency and power, magnetic field strength and geometry, and neutral argon pressure. It is concluded that at moderate power (~20 W), electron cyclotron resonance is important in the power absorption process.

The Effect of Low-Intensity Static Magnetic Field on Ni-P-PTFE Electroless Composite Plating Coatings

2016 ◽  
Vol 717 ◽  
pp. 112-117
Author(s):  
Jun Ying Hou ◽  
Hong Jiang Gao ◽  
Xiao Lin Liu ◽  
Yu Jiao ◽  
Li Liu
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Composite Coating ◽  
Magnetic Field Strength ◽  
Composite Coatings ◽  
Magnetic Field Direction ◽  
Composite Plating ◽  
External Magnetic Field Strength ◽  
New Processing

A new processing concept has been developed to produce Ni-P-PTFE electroless composite coating. This method combines magnetic field and electroless composite plating techniques to prepare high-quality Ni-P-PTFE electroless composite coating. The influence of magnetic on composite plating process and coatings performance by changing some factors such as the plating time, magnetic field strength, magnetic field direction. The results indicate that the external magnetic field improved deposition rate and the PTFE particles content of composite coatings, meanwhile, some performances of composite coating like thickness, corrosion resistance, were effected by external magnetic field strength. Therefore, the method combines magnetic field and electroless completing techniques had a wide application prospect in the aspect of improving the properties of electroless composite coating.

Photomagnetic Medium as Weak Magnetic Field Sensor

2015 ◽  
Vol 230 ◽  
pp. 285-290
Author(s):  
Oleksandr Tychko
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Weak Magnetic Field ◽  
Magnetic Field Sensor ◽  
Strength Measurement ◽  
Field Sensor

Photoinduced nucleation in an external magnetic field is investigated. A possibility of a week magnetic field strength measurement is showed.

Enhanced Capture of Magnetic Microbeads Using Combination of Reduced Magnetic Field Strength and Sequentially Switched Electroosmotic Flow—A Numerical Study

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Debarun Das ◽  
Marwan F. Al-Rjoub ◽  
Rupak K. Banerjee
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Magnetic Field Strength ◽  
Electric Fields ◽  
Electroosmotic Flow ◽  
Separation Technique ◽  
Target Cells ◽  
Magnetic Microbeads

Magnetophoretic immunoassay is a widely used technique in lab-on-chip systems for detection and isolation of target cells, pathogens, and biomolecules. In this method, target pathogens (antigens) bind to specific antibodies coated on magnetic microbeads (mMBs) which are then separated using an external magnetic field for further analysis. Better capture of mMB is important for improving the sensitivity and performance of magnetophoretic assay. The objective of this study was to develop a numerical model of magnetophoretic separation in electroosmotic flow (EOF) using magnetic field generated by a miniaturized magnet and to evaluate the capture efficiency (CE) of the mMBs. A finite-volume solver was used to compute the trajectory of mMBs under the coupled effects of EOF and external magnetic field. The effect of steady and time varying (switching) electric fields (150–450 V/cm) on the CE was studied under reduced magnetic field strength. During switching, the electric potential at the inlet and outlet of the microchannel was reversed or switched, causing reversal in flow direction. The CE was a function of the momentum of the mMB in EOF and the applied magnetic field strength. By switching the electric field, CE increased from 75% (for steady electric field) to 95% for lower electric fields (150–200 V/cm) and from 35% to 47.5% for higher electric fields (400–450 V/cm). The CE was lower at higher EOF electric fields because the momentum of the mMB overcame the external magnetic force. Switching allowed improved CE due to the reversal and decrease in EOF velocity and increase in mMB residence time under the reduced magnetic field strength. These improvements in CE, particularly at higher electric fields, made sequential switching of EOF an efficient separation technique of mMBs for use in high throughput magnetophoretic immunoassay devices. The reduced size of the magnet, along with the efficient mMB separation technique of switching can lead to the development of portable device for detection of target cells, pathogens, and biomolecules.

scholarly journals Flow behavior of cementitious-like suspension with nano-Fe3O4 particles under external magnetic field

2021 ◽  
Vol 54 (6) ◽  
Author(s):  
Dengwu Jiao ◽  
Karel Lesage ◽  
Mert Yücel Yardimci ◽  
Caijun Shi ◽  
Geert De Schutter
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
High Magnetic Field ◽  
Apparent Viscosity ◽  
Flow Behavior ◽  
Limestone Powder ◽  
Powder Suspension ◽  
The Magnetic Field

AbstractThe flow behavior of cementitious-like (limestone powder) suspension containing nano-Fe3O4 particles at constant shear rate of 10 s−1, characterized by the evolution of apparent viscosity over time, is investigated under various magnetic fields. Results show that the limestone powder suspension at flow-state exhibits remarkable magneto-rheological responses, reflected by a significant increase in the apparent viscosity after applying an external magnetic field. A higher field strength corresponds to a more rapid and pronounced response. The apparent viscosity experiences a sudden alteration with the stepwise change of the magnetic field due to the formation or disintegration of magnetic clusters. Linearly increasing magnetic field strength at low ranges (e.g. 0 T–0.3 T) shows less influences on the evolution of apparent viscosity, while at relatively high magnetic field, the apparent viscosity gradually increases with the magnetic field strength and the increase rate is comparable to that obtained under constant high magnetic field of 0.75 T. When the magnetic field is removed, the apparent viscosity exhibits a sharp reduction. If the magnetic field strength linearly decreases to zero, however, the apparent viscosity continuously increases until reaching a peak and then gradually decreases. This research shows in different ways how a desired apparent viscosity level of a cementitious-like suspension can be reached by means of an external magnetic field.

scholarly journals Observations and Models of Magnetic Molecular Clouds

1990 ◽  
Vol 140 ◽  
pp. 309-313
Author(s):  
P.C. Myers ◽  
A.A. Goodman
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Strength ◽  
Internal Structure ◽  
Magnetic Field Strength ◽  
Molecular Cloud ◽  
Molecular Clouds ◽  
Paper Briefly

In the last few years our knowledge of the strengths and directions of magnetic fields in molecular clouds has increased significantly. This paper briefly reviews observations of magnetic field strength and direction, compares such observations with equipartition models, and discusses the implications of these comparisons for the typical internal structure of the field in a molecular cloud.

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