A magnetorheological fluid (MRF) performs differently under different magnetic field strength. This study examined the fretting friction and wear characteristics of MRFs under a range of magnetic ...field strengths and oscillation frequencies. The fretting friction and wear behaviors of MRF are investigated using a fretting friction and wear tester. The surfaces of specimen are examined by optical microscopy and 3D surface profilometer before and after the tests and wear surface profiles, the wear volume loss and wear coefficient for each magnetic field strength are evaluated. The results show that the friction and wear properties of MRF change according to the magnetic field strength and oscillation frequency.
•Fretting friction and wear characteristics of MRF is examined.•The friction coefficients increased with increasing magnetic field strength.•The coefficient of friction decreased with increasing oscillation frequency.•Wear volume and coefficient become worse with increasing magnetic field strength.
Previous studies have shown that under some conditions, noise fluctuations in an fMRI time-course are dominated by physiological modulations of the image intensity with secondary contributions from ...thermal image noise and that these two sources scale differently with signal intensity, susceptibility weighting (TE) and field strength. The SNR of the fMRI time-course was found to be near its asymptotic limit for moderate spatial resolution measurements at 3 T with only marginal gains expected from acquisition at higher field strengths. In this study, we investigate the amplitude of image intensity fluctuations in the fMRI time-course at magnetic field strengths of 1.5 T, 3 T, and 7 T as a function of image resolution, flip angle and TE. The time-course SNR was a similar function of the image SNR regardless of whether the image SNR was modulated by flip angle, image resolution, or field strength. For spatial resolutions typical of those currently used in fMRI (e.g., 3 × 3 × 3 mm
3), increases in image SNR obtained from 7 T acquisition produced only modest increases in time-course SNR. At this spatial resolution, the ratio of physiological noise to thermal image noise was 0.61, 0.89, and 2.23 for 1.5 T, 3 T, and 7 T. At a resolution of 1 × 1 × 3 mm
3, however, the physiological to thermal noise ratio was 0.34, 0.57, and 0.91 for 1.5 T, 3 T and 7 T for TE near T2*. Thus, by reducing the signal strength using higher image resolution, the ratio of physiologic to image noise could be reduced to a regime where increased sensitivity afforded by higher field strength still translated to improved SNR in the fMRI time-series.
The novel controllable behaviour of magnetorheological (MR) fluid is the backbone of magnetorheological fluid-based finishing processes. MR fluid-based finishing processes facilitate better control ...over finishing forces as the stiffness of MR finishing fluid used in these processes can be controlled in accordance with the applied magnetic field and MR finishing fluid composition. Therefore, a detailed experimental investigation was carried out to find the effect of MR finishing fluid constituents on its yield stress through the Taguchi Design of Experiments. Rheological data obtained from a magneto-rheometer (MCR-102) was characterised by using Bingham plastic, Herschel–Bulkley and Casson’s fluid constitutive modelling. The coefficient of regression (R2) values of Herschel–Bulkley model were found to be best suited for all compositions of MR finishing fluid. Analysis of variance (ANOVA) has been used to find the contribution of selected parameters for improving the response characteristics. The optimized fluid has been then used for the finishing of biocompatible stainless steel AISI 316L, and the finishing results show that the average surface roughness value decreases down to 58 nm.
Sunspots are concentrations of magnetic field on the visible solar surface that strongly affect the convective energy transport in their interior and surroundings. The filamentary outer regions ...(penumbrae) of sunspots show systematic radial outward flows along channels of nearly horizontal magnetic field. These flows were discovered 100 years ago and are present in all fully developed sunspots. By using a comprehensive numerical simulation of a sunspot pair, we show that penumbral structures with such outflows form when the average magnetic field inclination to the vertical exceeds about 45 degrees. The systematic outflows are a component of the convective flows that provide the upward energy transport and result from anisotropy introduced by the presence of the inclined magnetic field.
•An optical fiber magnetic field sensor was constructed by incorporating magnetic fluid and a core–cladding–mode interferometer.•The sensing performances of the sensors are controllable by designing ...the parameters of the asymmetric-tapered structure.•The sensitivity of sensor with axial offset of 168μm and taper waist diameter is ∼162.06pm/mT ranging from 0 to 21.4mT.
We report an optical fiber magnetic field sensor by merging the advantages of magnetic fluid and a core–cladding–mode interferometer which is directly fabricated on a standard single-mode fiber by using an arc fusion splicing machine. The sensing performances of the sensors are controllable by designing the parameters of the asymmetric-tapered structure. Experimental results show that the sensor with axial offset of 168μm and taper waist diameter of 45μm not only has good optical properties but also a relatively high magnetic-field sensitivity of ∼162.06pm/mT ranging from 0 to 21.4mT. The proposed sensors would find potential applications in weak magnetic sensing fields.
In this study, non‑hydrogenated diamond like carbon (DLC) coatings were deposited by sputtering a graphite target in argon (Ar) by high power impulse magnetron sputtering (HiPIMS) using deep ...oscillation pulses. The effects of the magnetic field strength (B) tangential to surface of the target racetrack on the deposition parameters were studied. The structure, adhesion, and mechanical properties of DLC coatings deposited at different B were investigated by scanning electron microscopy (SEM), Raman spectroscopy, atomic force microscopy (AFM), scratch test, and nanoindentation. The tribological properties of the DLC coatings were evaluated using ball on disk wear test under dry and lubricated test conditions. It was found that the peak target current and substrate current density increased as B increased due to the enhanced electron confinement which results in an increased ionization efficiency. The enhanced ion bombardment was beneficial for improving the structure and properties of DLC coatings. As B increased, the DLC coatings exhibited more compact structure, smaller carbon mounds, and higher sp3 bond fractions. The improvement of the microstructure of the DLC coatings contributed to improved hardness and wear resistance of the coatings in both dry and lubricated test conditions. However, the deposition rate decreased at higher B owing to the high probability of back-attraction of carbon ions. The results suggested that controlling B in the range of 600 G to 700 G is important for achieving fully dense structure, high sp3 bond fractions, and high hardness for the DLC coatings deposited using HiPIMS. A further increase in B to 850 G showed no significant changes in the magnetic field induced effects on the structure and properties of the coatings.
•A stronger magnetic field increased peak target current and substrate current density in HiPIMS.•An ideal magnetic field for HiPIMS DLC coating depositions was between 600 G and 700 G.•Further increasing the magnetic field to 850 G showed limited benefits.•The deposition rate of HiPIMS decreased as the magnetic field strength increased.
In this article, we propose a magnetic field sensor based on a multimode-D-type-multimode (MMF-D-type-MMF) fiber structure employing surface plasmon resonance (SPR). The sensor's surface is coated ...with a layer composed of indium tin oxide (ITO), silver (Ag), and a 2-D material known as Bi2O2Se. Bi2O2Se exhibits varying magnetic permeability within a specific magnetic field strength range, a characteristic confirmed in practical tests. To enhance the sensor's sensitivity to magnetic fields, we implemented several optimization measures. These measures encompassed adjustments to: 1) the concentration of the magnetic fluid (MF); 2) the thickness of the Bi2O2Se layer; and 3) the selection of fiber type. We conducted simulations and experimental tests to refine these parameters. Consequently, the proposed D-type sensor demonstrates a sensitivity of 0.4325 nm/GS within the 40-150 GS magnetic field strength range, representing a significant 75.31% sensitivity improvement achieved through the aforementioned enhancement measures. When compared to other fiber-optic magnetic field sensors, our proposed sensor stands out for its exceptional sensitivity, straightforward design, robust repeatability, strong anti-interference capabilities, and high stability. As a result, it holds significant potential for a wide range of applications in aerospace, aviation, environmental monitoring, and related fields. The sensor has a high sensitivity in the range of 40-150 GS, which can monitor the magnetic field strength in life in real time and determine whether it meets the human body safety magnetic field standard.
This study aims at investigating the impact of using the Magnetorheological Elastomers (MREs) medium to improve the formability of T-shaped Inconel 718 tubes during the bulging process. Besides, the ...influence of the punch size and the intensity of the magnetic field on the branch height and wall thickness distribution of the T-shaped Inconel 718 tubes are also explored. The results showed that the parts formed by the punch with a length of 5 mm in the pressurization zone have better forming quality. The external magnetic field can promote a high branch, and by increasing the intensity of the magnetic field, the branch height was increased and then decreased. At the same time, the magnetic field reduced the amount of material accumulation between the guiding zone and the bulging zone. Besides, it promotes the material in the guiding zone to enter the bulging zone and improve the bulging ability of the T-shaped tube.
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