Cubic perovskite-type Mn₄C is difficult to prepare for its metastable characteristics. In this work, we have obtained high-purity Mn₄C successfully by using melt-spinning method. The effects of stoichiometry on the structure and magnetic properties of the samples were studied systematically. We found that x = -0.1 is the optimum composition for the formation of the cubic perovskite phase in Mn_4+xC during rapid quenching. Most Mn_4+xC melt-spun ribbons with x other than -0.1 are composed of Mn₂₃C₆, α-Mn, and Mn₄C, while the fraction of different phase in Mn_4+xC ribbons varies with x. The Curie temperature of Mn_4+xC ribbons increases slightly with decreasing x, which may affect the lattice parameters of cubic Mn₄C and thus the Mn-Mn exchange interactions. The magnetization of Mn_4+xC (x = -0.1 and 0) increases with increasing temperature in high-temperature region while the onset temperature for such behavior is dependent on the fraction of Mn₄C in the samples.

In order to solve the problem of low damping force caused by low utilization of magnetic field in traditional magnetorheological dampers, a hybrid channel valve type magnetorheological damper with circular channel and disk channel are proposed. The main content of this paper is to design the basic structure of mixed channel valve magnetorheological damper. The mathematical model of damping force based on Bingham plastic model was established from the design of magnetic circuits. The two-dimensional simulation model of MR Damper was established by using EMAG module in ANSYS finite element analysis software, and the magnetic circuit of mixed channel valve MR Damper was simulated and analyzed. The results show that the output damping force of the hybrid channel valve-type magnetorheological damper is 18 KN and the adjustable coefficient is 14.52 with the current I of 3A, the number of coil turns of 560, the axial damping gap of 1 mm and the radial damping gap of 1.5 mm.

The fluid flow under the slip effects present many dynamical applications in petroleum engineering, soil sciences, aerodynamics, thermal systems etc. The aim of current investigation is to observe the heat transfer phenomenon in magnetized flow of viscous fluid due channel with lower unbend wall. The fluid flow is altered due to interaction of slip effects. The injection phenomenon for porous medium has been considered. For heat transfer investigation, viscous dissipation applications are endorsed. The fundamental problem is modelled with associated laws. The variational iteration method (VIM) scheme is proposed to simulate the analytical outcomes. The numerical results for Nusselt number and skin friction coefficient are depicted and analysed graphically. The summarized observations convey that control of heat transfer is improved with interaction of slip phenomenon. The declining result for Nusselt number is referred to suction parameter.

The thermal flow of second grade fluid with Soret and Dufour effects has been observed in this investigation. The problem is modified with mixed convection and thermal radiation applications. The thermal conductivity with variable relations is used to analyze the transport phenomenon. Further, the applications of mixed convection and magnetic force has also been focused. The convective thermal and concentration flow constraints are used for the current flow problem. The shooting numerical scheme is used to calculate the numerical observations. The major impact of parameters is visualized for flow parameters. It is observed that the velocity profile increases for curvature parameter and viscoelastic fluid parameter. The assumptions of variable thermal conductivity enhanced with transport phenomenon. The Nusselt number declined for variable thermal conductivity parameter.

Density functional theory calculations provide very accurate physical quantities at zero Kelvin. Nonetheless, it is necessary to understand how the physical quantities are changed at finite temperatures for real device application purposes. Here, we investigate the finite temperature dependent magnetic properties of hole doped 2H-VSe₂ bilayer structure using atomistic simulation. We find that the Curie temperature of 600 K at the hole concentration of 2.27×10²⁰ cm^-3, and this is enhanced to 620 K at the hole concentration of 3.01×10²⁰ cm^-3. We fit the temperature dependent magnetization curve (M(T)) using both Curie-Bloch and Kuz’min equations. We also calculate temperature dependent magnetic anisotropy energy. We find that the magnetic anisotropy energy is almost linearly decreased with increasing temperature. Besides, we obtain that the normalized temperature dependent anisotropy constant [K(T)/K(0)] shows the relation to the temperature dependent magnetization curve of [M(T)/M(0)] ^2.9, and this is well converged with the exponent of 2.9 in the Callen-Callen theory.

For a novel Vernier-gimballing magnetically suspended flywheel (Vernier-gimballing MSFW) with conical magnetic bearing (MB) and Lorentz MB, the rotor’s dynamic model is constructed based on the characteristics of both coupling torque generated by conical MB and nonlinear titling torques generated by Lorentz MB. To make the high-speeding rotor tilt precisely and fast to output large moment, the Vernier-gimballing control method based on the extended state observer (ESO) combined with feedback linearization is presented originally considering torques’ complex nonlinearities, and the sliding mode control (SMC) with ESO is designed to improve the robustness of the closed-loop system. Simulations and experimental tests to verify the rightness and validity of SMC with ESO have been done and all research results indicate that the rotor can track the tilting signal faster and more accurately than classic SMC to output high precision moment.

Fourier-transform-based velocity-selective (FT-VS) magnetization preparation has shown great promise for unenhanced MR angiography and arterial spin labeling. Although recent technical advances made FT-VS preparation resistant to B₀ and B₁ field inhomogeneity, there remain other non-ideal conditions including tissue relaxation, eddy currents, and accelerated motion, which are often ignored during excitation pulse design. In this study, using a double-refocused VS preparation pulse as a testbed, excitation profiles were numerically simulated taking into account the potential effects of the three non-ideal conditions. The longitudinal magnetization of arterial blood resulting from FT-VS preparation turned out to decrease from the ideal value of M₀ to 0.92M₀, 0.99M₀, and 0.88M₀ due to tissue relaxation, eddy currents, and accelerated motion, respectively. When all three factors were considered simultaneously, the worst-case relative contrast ratio (CR) between arterial blood and muscle tissue was estimated as 0.86, corresponding to a decrease by 14 % from the ideal CR of 1.0.

The purpose of this study was to confirm the utility of block-matching and 3D filtering (BM3D) algorithm in computed tomography (CT) images using a tin filter with a high pitch. We acquired phantom images and measured the coefficient of variation (COV) and contrast-to-noise ratio (CNR) for quantitative evaluation. The optimized results were obtained when the sigma value of the BM3D algorithm was nine. In addition, when the sigma value of the optimized BM3D algorithm was applied, superior results were obtained compared with conventional filtering methods. In particular, we confirmed that the COV and CNR of the images obtained using the BM3D algorithm improved 6.52 and 5.49 times, respectively. In conclusion, the utility of the optimized BM3D algorithm has been demonstrated in low-dose CT images using a tin filter.

For magnetic field calculations, cylindrical permanent magnets are often approximated as ideal, azimuthally symmetric solenoids. Despite the frequent usage of this approximation, research papers demonstrating the validity and limitations of this approach are scarcely available. In this paper, the experimentally derived magnetic field of a cylindrical permanent magnet is compared with the semi-analytically calculated magnetic field of an ideal solenoid. An experimental setup for measuring the magnetic field distribution is demonstrated and employed for gathering the data. The proposed setup allows to measure the distributions of the axial and radial components of the magnetic field surrounding the magnet. In addition, we calculated the magnetic field using the FEM method and compared it with the solution of an ideal solenoid and discussed the obtained deviation.

The structural property, bulk density and porosity of V₂O₅ (0.0, 0.4, 0.8 and 1.2 wt.%) added Li-Zn ferrites are observed along with the surface morphology. The samples have been prepared by the solid-state reaction technique and sintered at 1050 ℃. The X-ray diffraction patterns of the prepared samples have shown the single phase cubic spinel structure. A microstructural study demonstrates that the grain size increases up to 0.8 wt.% V₂O₅ and slightly decreased thereafter for 1.2 wt.% V₂O₅ addition. The saturation magnetization value increases from 44.0 to 50.3 emu/g as the V₂O₅ content increases up to 0.8 wt.%. The decrease of magnetization for 1.2 wt.% V₂O₅ content is apparent and it is found to be 47.3 emu/g. This may be related to the dilution effect with the excess of non-magnetic V₂O₅. It is also observed that the value of initial permeability increases up to 0.8 wt.% V₂O₅.

Ferrofluids as a new kind of nano-functional material, possessing both magnetism of solid material and fluidity of liquid material, thus, they have extensive scientific research and engineering application value. To avoid the defects of conventional non- or single silane coupling agent in silicone oil-based ferrofluid preparation, TEOS and KH-792 were introduced as surfactants to modify Fe₃O₄ magnetic nanoparticles (MNPs). Silicone oil modified by carboxylic acid was used as based liquid because of improved compatibility with surfactants. Silicone oil-based ferrofluid was prepared by high-energy ball milling method, and its rheological properties were studied. The saturated magnetization of the silicon oil based ferrofluid was 142.71 Gs. When external magnetic field was applied, the MNPs formed a chain structure in the microscope. The viscosity of ferrofluid increased with magnetic field and the shear stress rose with shear rate. The viscosity decreased steeply with increasing temperature and shear rate. The viscosity of silicone oil-based ferrofluid was 950 mPa·s at 25 ℃ and can vary from 2044 mPa·s at 5 ℃ to 465 mPa·s at 40 ℃. The ferrofluid transformed from a Newtonian fluid at zero magnetic field to a shear-thinning pseudoplastic Bingham fluid when an external magnetic field was applied. The viscosity varied from 1.37 to 2.38 × 10⁵ mPa·s at zero shear rate. While, when magnetic field varied from 0 kA/rose to 160 kA/m, the viscosity increased obviously and this phenomenon became more pronounced as the shear rate decreased. When magnetic field intensity was higher than 64 kA/m, the viscosity increased slowly with increasing shear rates and viscosity curve was close to a straight line at 100 s^-1. This study expands the idea of exploring the synthesis of ferrofluids with mixed surfactants. Silicone oil-based ferrofluid is expected to have unique application prospects in the aerospace field, especially in space damping, sealing and biomedicine.

The entropy of electron-positron and ion plasma plays a significant role in the transportation of particles, momentum, and energy. Drift waves in these plasmas produce central mechanisms for this transport. The effects on tri-polar and quadrupolar vortexes in epi plasma have been analyzed numerically under various approximations. As plasma consists of various elements, it is important to understand the effects of entropy on systems. In this article, we have discussed how entropy affects linear and non-linear equations in the presence of temperature, equilibrium density, electrostatic potential gradients, and a magnetic field. Additionally, by investigating tri-polar and quadrupolar vortexes without regard for entropy effect we can find information about this phenomenon.