In this paper, a method is introduced to directly calculate the reluctances of fringing fields in analyzing a magnetic equivalent circuit model for an axisymmetric solenoid actuator including radial air gaps as well as axial air gaps. The introduced method was motivated by the possibility to calculate the cross section area depending on the radial position of an infinitesimal element when the infinitesimal element is defined to be integrated in the flux flow direction in a circular-arc straight-line model of an axisymmetric model. In this method, the reluctance of fringing field near an air gap can be calculated directly. For an objective model, the MEC analysis was performed using the introduced method and an iterative method. In the iterative method, the nonlinearity of the ferromagnetic material parts is resolved. In order to validate the introduced method, MEC analysis and FEA results are compared. And for validating the method in a view of computation also, an optimized design satisfying pre-defined constraints was searched using MEC analysis, and then the results of the MEC analysis using the introduced method and FEA results are compared for the searched design and the initial design.

In this work, we controlled the magnetic properties and water-solubility of CoFe₂O₄ nanoparticles by adjusting the reaction conditions during the preparation process. The growth condition-dependent crystalline, microstructure and therefore their magnetic properties were investigated in detail. It is found that the crystalline and the size of the nanoparticle become larger with the increasing of both the reaction temperature and reaction time. Consequently, the saturation magnetization (Ms) of our products was highly improved. Specifically, the typical sample prepared at 180 ℃ for 2 h, which has a higher Ms and good solubility in water was chosen as an alternative agent in magnetic resonance imaging The results show that it is an effective T₂ weighted MRI contrast agent.

A temperature-dependent micromagnetic study has been conducted to examine the spin dynamics of the perpendicularly magnetized nanodot in a thermally induced magnetic switching (TIMS) scheme. The magnetic parameters used in this study represent the properties of BaFe. The impact of writing-temperatures below the Curie point on the magnetization reversal characteristic of nanodot with three damping levels, which related to the minimum writing-field as well as the zero-field-switching probability, were discussed systematically. The spins configuration of the nanodot was also presented to visualize the modes of the magnetization switching. The simulation reveals that the writing-field decreases concerning with the writing-temperature and reaches its lowest value at the temperature of 0.4 % below its Curie point. During the heating phase, the mechanism of demagnetization is coupled with the writing-temperature. Meanwhile, the magnetic damping takes over the role in the magnetic switching mechanism during the freezing.

The motor core stress produced during the manufacturing process and motor operation changes the electromagnetic characteristics of the iron core. Thus, research on electromagnetic calculations under the condition of stress is one of the key challenges to achieve more efficient designs of permanent magnet motors. In this paper, the stress equations of a rotor centrifuge and stator interference assembly are studied, and the changing regularity of stress and magnetic properties of electrical steel and its causes are analyzed theoretically. A device for measuring the stress and magnetic properties of electrical steel is designed and tested. Then, a model for iron loss calculations that includes stress is proposed for improved design. The effects of stress on loss, d-q axis inductance, and torque are simulated and compared using an IPMSM as an example. The feasibility and accuracy of this method are verified by comparing the simulation and prototype test results.

Magnetic fluid has many technical applications and many new ones are being developed. One of the applications is in magnetic fluid seals. This publication describes the new phenomenon of the magnetic fluid seal reseal mechanism, discovered while carrying out research. This phenomenon is manifested by the pressure oscillation medium being sealed, which results from the instability (cyclic destruction and rebuild of the liquid ring) in the magnetic fluid seal. It occurs in an inhomogeneous magnetic field and, in this case, is caused by the eccentricity of the seal components. In order to study this mechanism, magnetic fluid characterized by different physical properties was selected. Numerical simulations were performed to determine the magnetic field distribution in the seal. Research results showed the possibility of measuring the eccentricity of the magnetic fluid seal elements. Studies have shown that it is possible to determine the displacement of about 0.01 mm.

Composite hard magnet NdFeB materials were made using powdered rapidly quenched Nd-Fe-B (MQP-B) and polymers (bakelite). The proportion of the polymer matrix was varied (2.0, 5.0, 7.0, and 10 wt.%). The composite hard magnet NdFeB materials were compacted using one-sided uniaxial hot pressing at 160 ℃ for 20 min. The bulk density of the composite hard magnet NdFeB was measured using the Archimedes method. Compression tests were carried out using the Universal Testing Machine. The results show that a permanent magnet composite with a 2 wt.% bakelite binder composition exhibits higher bulk density and superior magnetic parameters (i.e., remanence, coercivity, and energy product), but slightly lower compressive strength of approximately 845 kgf/cm².

The effects of adding Gd on the Curie temperature (T_C), glass-forming ability (GFA), and magnetocaloric effect (MCE) were studied in Fe_68-xGd_xTb₅B₂₃Nb₄ (x = 0, 2, and 6) glassy alloys prepared by suction casting. It was shown that when Gd content was exchanged with Fe partially for x = 2, GFA was increased, whereas for x = 6, adding Gd content has reduced the GFA and amorphous structure could not be obtained. Critical diameter was found to be 3 mm for Fe₆₆Gd₂Tb5B₂₃Nb₄ bulk metallic glass (BMG). By exchanging Gd with Fe partially, T_C could effectively be tuned in a quite broad temperature interval from 487 K (x = 0) to 380 K (x = 6) for which amorphous structure could not be obtained. Maximum magnetic entropy change (−ΔS_M)^max values were found to be 1.16, 0.84 Jkg⁻¹K⁻¹, and 0.54 Jkg⁻¹K⁻¹ as well as, refrigeration capacity (RC) values were obtained as 116 J/kg, 84.84 J/kg, and 40.50 J/kg under a low field change of 2 T for x = 0, 2, and 6, respectively. Although T_C was shifted to lower temperatures by exchanging Fe with Gd partially, −(ΔS_M)^max decreased almost half of the base alloy and RC decreased approximately 1/3 of the base alloy.

In this study, ferrofluids were prepared by colloidal dispersion of paramagnetic Fe₃O₄ nanoparticles coated with long-chain carboxyl terminated silicone oil in silicone oil. Effect of pH value of the aqueous solution on coating was investigated. The IR and TG analysis indicated that acid conditions favored the coating of carboxyl terminated silicone oil. Stabilities of ferrofluids were characterized by density change and mass specific saturated magnetization change during centrifugation and static settlement observation. The static settlement observation indicated that the prepared silicone-oil-based ferrofluids have better stability than unmodified and oleic acid modified ferrofluids. Finally, the magnetic properties and stability of ferrofluids with different particle mass fraction were characterized.

A previous trigger assembly with a single embedded permanent magnet has malfunction problems such as the generation of a virtual trigger signal by an external magnetic field. In this study, we improved a trigger assembly, which can minimize the influence of external magnetic field. In order to improve the trigger assembly, two designs were considered. Through an M&S study for the optimal characteristics of Hall-effect sensor, we confirmed that the magnitude of the driving magnetic field of the Hall-effect sensor should be at least 50 gauss for the application of a trigger assembly. The second design was a magnetic bipolar simultaneous recognition system with a time-interval of 10 ms, which occurs when two embedded permanent magnets with different polarities are recognized simultaneously. As a result, the improved trigger assembly, which reflects the two design results, excluded the malfunction of small arms by the external magnetic field without magnetic shielding.

This paper comprises the exact solutions of Non-Newtonian multiphase fluid through peristaltic pumping characteristics in an annulus having complaint walls and applied magnetic field. The mechanics of the geometry are defined cylindrical due to its large number of utilizations in medicine and biological apparatus. The external cylinder is having sinusoidal waves travelling along its walls. The problem is simplified by some suitable and valid approximations. The authors have obtained the accurate solutions of the velocities of two phases. The effects of appertaining parameters have been displayed through graphs of velocity for v and particulate phases and the behavior of curves are manipulated accordingly. It is concluded that applied magnetic field decreases the velocity of both the fluid and the particles flow.

This study aimed to compare the magnetic resonance imaging (MRI) and computed tomography (CT) techniques for the measurement of visceral adipose tissue (VAT). Twenty-five male subjects who underwent CT and MRI imaging within 30 days were included in the study and reviewed by the Institutional Review Board. For MRI, 3.0 Tesla Achieva TX (Philips Medical Systems) was used, and for CT imaging, a 64 channel detector (Lightspeed VCT, Discovery HD 750) was used. VAT was measured at the umbilical level. Cut-off values of Hounsfield units in the range of -50 to -250 were assigned for adipose tissues in the CT images, and the crosssectional distance ratios were used with MRI scanning. The mean difference in total adipose tissue (TAT) between CT (mean: 21711.7 ± 5232 mm³) and MRI (mean 21445.5 ± 4882 mm³) was 266 mm³, Also, the mean difference in VAT between CT (mean 10133.8 ± 2304 mm³) and MRI (mean 10143 ± 2107 mm³) was 9.6 mm³. The two images were highly correlated with TAT: R² 0.90 (p < .01) and VAT: R² 0.90 (p < .01). The VAT measured using MRI showed high similarity with the CT image, good reproducibility of soft tissue image, and excellent quantitative value of abdominal obesity.

This article investigates the unsteady flow of a viscous fluid over a magnetized moving plate emerging from a moving slot. This new family of unsteady boundary layer flow behaves similar to stretching and shrinking sheet problems depending upon the motion of the slot. The governing partial differential equations are reduced to correct similar form using the Blasius-Rayleigh-Stokes variable. Effects of moving slot and magnetic field on important physical quantities are examined. An interesting observation was the influence of magnetic field on the existence of dual solution for the range of moving slot parameter.

The present article is planned theoretically to throw light on non-Newtonian Casson liquid flow and heat transport analysis over an exponentially stretching sheet with second-order velocity slip condition. The analysis of magneto-hydrodynamic (MHD) is an important interdisciplinary field. One of the most imperative applications related to engineering problems is plasma confinement, liquid-metal cooling of nuclear reactors, and electromagnetic casting. The flow here is considered to be electrically conducting. The modelled equations of mass, momentum and energy transport are reduced into the nonlinear ordinary differential equations by employing a similarity approach which are then solved numerically by employing finite difference collocation process (a three-stage Lobatto IIIa scheme). The inspiration of convergence flow parameters on dimensionless velocity, temperature have been discussed graphically. The obtained results confirm that an excellent agreement is achieved for the Newtonian case with those available in the literature. Consequences establish that skin friction rises in the presence of Casson fluid parameter and the Nusselt number show enhancement for second order slip parameter.

Purpose: This study aimed to present a protocol for constructing MRS phantoms that are supposed to be subjective of spectroscopy using 1.5T machines. Methods: As phantom containers, laboratory clear/amber glass bottles and an internally-designed Plexiglass and PVC cylinders were tested to evaluate the effect of phantom material and design on produced signals. HPLC and distilled-water were evaluated as solvent of metabolites. Finally, a protocol was suggested. Results: The results revealed that the physical walls of internally-designed phantom affect the WS and its baseline noise. The results also showed that even the amber-pigments inside the bottles can affect the MRS signal. Accordingly, the combination of HPLC-water inside clear-glass containers is suggested. Conclusion: The suggested protocol is as follows, apply clear-glass container as phantom body, do not build internal-structures using physical walls of glass or any other materials. Apply HPLC-water as solvent instead of distilled-water. Check the purity of chemical metabolites.

A LiFePO₄ was prepared using the ball milling. The X-ray diffraction patterns of the sample were measured, and the results confirmed that the sample’s structure was orthorhombic with space group Pnma. The particle size and morphology of the sample prepared by the ball mill method confirmed by FE-SEM. The magnetization curves of the sample were measured using a vibrating sample magnetometer at temperatures of 4.2 to 295 K at 1000 Oe. The Néel temperature (T_N) and spin-reorientation temperature (T_S) were found to be 51.5 and 25 K, respectively. We investigated the magnetic hyperfine interaction using Mössbauer spectrometry at various temperatures between 4.2 and 295 K. At temperatures below T_N, the Mössbauer spectra of the sample were exhibited eight absorption lines resulting from the magnetic dipole and electric quadruple interaction. The Fe ions state of sample at all temperatures were found to be ferrous state (Fe²⁺) ions. Debye temperature (θ_D) of 433 ± 5 K was obtained for the sample. The permeability and permittivity were obtained using a Network analyzer.

We designed a voltage-control spintronics memory unit-cell, VoCSM, with high write-efficiency to prove a potential to reduce writing energy per bit. By optimizing a self-aligned structure, the cell has the critical switching current (I_csw) smaller than 50 μA at 20 nsec. for designed MTJ size of about 50 × 150 nm². The value is much smaller than that for mature STT-MRAM with the similar dimension. VoCSM also was proved to have unlimited endurance. Finally, with an empirical equation of I_csw further reduction of I_csw is estimated to clarify that VoCSM has a potential to reduce I_csw down to several μA.

The wireless power transfer (WPT) using magnetic resonance coupling method has been known to have the advantage of being able to transfer power across large air gap with considerably high efficiency. As well as, as such a method can eliminate the physical contact loss in the system, it provides an ideal solution for the problem of contact losses in the power applications. From these reasons, WPT technology has started to be applied to the wireless charging for various power applications such as transportations (train, underwater ship, electric vehicle). In the high speed superconducting magnetic levitation (MAGLEV) train, antenna (Tx) coils, which are installed both sides of train, are placed on the guidance rail, as well as, superconducting receiver (Rx) coils can be installed in traveling train. In the superconducting system, a cooling vessel, which is made by steel materials, is a requisite subsystem. However, since the steel materials can shield electromagnetic field, the structure design of cooling vessel can affect the transfer efficiency. In this study, we presented transfer efficiency and operating characteristics from copper Tx to superconducting Rx coil under different structures of cooling vessel with radio frequency power of 370 kHz below 500 W.

The purpose of present study is to observe the change in capillaroscopic features before and after pulsed magnetic field (PMF) stimulus: the number, shape, length of capillary loop, and diameters of efferent capillary, and images of capillary loop. Nailfold capillary microscopy was used to quantitatively estimate the change of morphological characteristics of the capillaries. Capillary blood flow is recorded using video camera recorded at a frame rate of 60fps attached to the microscope. The velocities of capillary blood cell were 441 ± 22 and 508 ± 20 μm/s, before and after PMF stimulus, respectively. For the nailfold capillary morphologies, compared to before PMF, the more clearly visible loops are arranged as well as the capillary loop lengthened after PMF stimulus. Also the numbers of capillary loop/mm increased after PMF stimulus. In addition, tortuous capillary turned to hairpin shaped loop and the number of tortuous and abnormal capillaries are reduced after PMF stimulus. Our results proved the PMF stimulus on the palm of left hand for 10 min. provide the improvement of capillary blood flow, and it decreases vascular resistance in the blood micro-circulatory system. In addition, our study suggested quantitative and qualitative parameters of the nailfold vasculature in order to elucidate the effect of PMF. For expanding our findings, we need to have more subjects across a wide spectrum of age and with microvascular abnormalities, such as scleroderma, dermatomyositis and related disorders.

The structural stability and magnetic properties of Mn_3+xAl_1-xC antiperovskite with varied Mn/Al substitution were studied systematically. Single phase Mn_3+xAl_1-xC alloys with antiperovskite structure were obtained in samples with x = −1/4, 0, 1/4, 1/2. An additional Mn₂₃C₆ phase was precipitated from Mn_3+xAl_1-xC antiperovskite for x = 3/4 while Mn₂₃C₆ phase was formed as major phase for x = 1. The mutual substitution of Mn and Al atoms has substantial effect on the Curie temperature and the saturation magnetization of the Mn_3+xAl_1-xC alloys. In comparison with the as-cast alloys, the as-annealed Mn_3+xAl_1-xC alloys exhibit reduced Mn/Al substitutions after high temperature homogenization, which enhances the ordering of Mn and Al atoms in the lattices. The Curie temperature of the homogenized Mn_3+xAl_1-xC increases with increasing Mn substitution to Al. The Mn₃AlC alloy shows the highest saturation magnetization among all samples with varied Mn/Al ratios. Most samples show zero coercivity and zero remanent magnetization. The maximum value of the magnetic entropy changes of Mn_2.75Al_1.25C at 285 K is 2.26 J/kg K in fields up to 3 T.

Drilling is traditionally performed by multi-motor systems manually. However, the complex intermediate transmission mechanisms in the traditional design have large size and relatively low robustness. In this paper, a splitstator 2-degree-of freedom (2DoF) machine is applied. By conducting linear, rotary, and helical motion by only one machine, it provides a more compact, more integrated, more reliable, and stronger-adaptability electrically drilling machine for submerged drilling systems. On account of the adoption of the split-stator structure, the electromagnetic design of such 2DoF machine is a significant challenge. In this paper, a design method for the 2DoF machine with special split structure is proposed based on the electric decoupled equivalent circuit (EDEC). Then a 1.5 kW 2DoF drilling machine is designed, and the electromagnetic performances are verified by the 3D finite element analysis (FEA). The results show the good characteristics and feasibility of applying the 2DoF machine in drilling systems.

In the design of squirrel-cage induction machines, torque pulsation and electromagnetic noise always exist. However, they cannot be minimized simultaneously with no matter which slot combination. Electromagnetic noise is aroused by the spatial harmonics in the air gap which are generated by stator magneto-motive force and rotor magneto-motive force. Generally, stator slot number cannot be changed while rotor slot number and slot size could be modified optionally. One set of uniform-bar rotor winding cannot solve this problem. To investigate this issue, this paper proposes a novel rotor winding connection topology for the simultaneous reduction of torque pulsation and electromagnetic noise. 2D finite element models with conventional rotor winding and novel rotor winding are simulated and compared.

Dual skewed rotor is an improved skewed rotor pattern in suppressing the slot harmonics. However, in order to lessen synchronous parasitic torque, the relevant structural parameters should be modified for different slot combinations. According to the unified expressions of magnetic flux densities, the general harmonic torque could be calculated with the virtual displacement method. Then, the synchronous torque ratio is proposed to reflect the effect of synchronous parasitic torque on the starting torque. Under the premise of the assumed parameter range, the rotor type and minimized skewed angle are determined for three kinds of slot combinations. The normal skewed rotor could be seen as a special topology of dual skewed rotor. Finally, the validity of designing process is verified by the comparison of simulation study and experimental results.

Zinc-doped cobalt ferrite magnetic nanoparticles (CoZnFe₂O₄) with silica encapsulation have been successfully synthesized by using coprecipitation method. The concentration of silica was varied by 0 %, 5 %, 10 %, 15 %, 20 %, 30 % and 50 % of weight. The XRD spectra show that all samples have the character of the main spinel diffraction peaks (2θ) attributed to the (220), (311), (400), (422), and (511) planes. The FTIR analysis shows that the intrinsic stretching vibrations of metal-oxygen at the frequency range of 393 cm⁻¹ - 401 cm⁻¹ and 470 cm⁻¹ - 563 cm⁻¹ were found at octahedral and tetrahedral sublattices, respectively. The unencapsulated CoZnFe₂O₄ nanoparticle has coercivity (Hc) and maximum magnetization (M) of 251 Oe and 29.0 emu/gram, respectively. The coercivity value of the encapsulated nanoparticles increases up to 853 Oe with the increase of silica concentration, while the maximum magnetization decreases to 24.2 emu/gram.

To solve the sedimentation drawback of soft-magnetic carbonyl-iron (CI) particles for their application to a magneto-rheological (MR) fluid, the coating of a polyindole (PIn) onto the surfaces of CI microspheres was introduced through chemical oxidization polymerization using 4-aminobenzoic acid as a grafting chemical to increase the interaction between CI particles and PIn. The coated morphology was confirmed using a scanning electron microscope, whereas the reduced density was examined through a gas pycnometer. The effect of the coating on MR performance was analyzed using a rotation rheometer connected with a magnetic field generator. Based on the results of a dynamic oscillation rheological test, the CI/PIn-based MR fluid exhibited a more elastically solid behavior with the applied magnetic fields when compared to a pure CI-based MR suspension, showing an increased magnetic-field strength-dependent storage modulus from a strain sweep test. With a solid-like behavior under an applied external magnetic field, the storage modulus was observed to be higher than the loss modulus within the entire frequency range.

Magnetic Fe₃O₄@polystyrene (PS) nanoscale composite particles were fabricated using a unique Shirasu porous-glass membrane technique and used as additives to a magnetorheological (MR) suspension with magnetic carbonyl-iron (CI) particles. The morphology of the fabricated Fe₃O₄@PS composites was characterized by transmission electron microscopy. The effects of the Fe₃O₄@PS composite particle additive on its MR behavior was examined using a rotation rheometer under an applied magnetic field. The results revealed improved MR behavior, such as higher storage and loss moduli, and elastic yield stress compared to those of the pure CI-based MR suspension under an external magnetic field.

We present an analytical method for applying conformal mapping to the notched geometry of a surface permanent magnet synchronous motor to calculate the cogging torque. First, the complex relative air-gap permeance (CRAP) of the notched air-gap is calculated by multiplying the CRAP of a slotted air-gap with the notch sensitivity coefficient, which is defined by the relation of slot and notch shapes. Secondly, the no-load air-gap flux density (AFD) is derived from the CRAPs of the notched and slotted air-gaps. Finally, the cogging torque of the notched motor is calculated by the no-load AFD and is verified using the 2D finite element analysis (FEA) result. A 4-pole and 12-slot surface permanent magnet synchronous motor with the notch is used herein.

This study investigates the design of a flux modulation pole (FMP)-type vernier motor considering irreversible demagnetization in a permanent magnet (PM). The FMP-type vernier motor, which has a distinct configuration compared to the conventional vernier motor, is taken into account because the PM placed at its stator is vulnerable to irreversible demagnetization. The demagnetization ratio of the PM is analyzed and compared using two different types of flux barrier, namely the bar- and delta-type barriers with varying design parameters. To guarantee reliability of the motor performance, both normal and abnormal operating conditions are considered for each type of flux barrier. Finally, selected models are compared to the base FMP-type vernier motor model in terms of demagnetization ratio and output torque.

The magnetic flux density of a rotor core is increased on the basis of the B-H characteristics of the core when the field current of a field-winding claw-pole type motor (FWCPM) is increased. However, owing to the saturation of the rotor core caused by the increase in magnetic flux density, the magnitude of the electromotive force relative to the field current increase in a nonlinear direction. Therefore, to improve the performance of the FWCPM, it is necessary to reduce the leakage flux and rearrange the source of the rotor in order to supply additional magnetic flux. In this paper, three types of ferrite assisted field-winding claw-pole type motors (FAFWCPM) are proposed to improve the nonlinearity and performance of the FWCPM field current. The magnets applied to the FAFWCPM are located between the claws, at the front of the claws, and at the tops and bottoms of the claws. Further, to ensure analytical accuracy, the amount of magnets used in the motor is equally limited. Finally, the magnitude of the electromotive force under a no-load condition and the average torque under the load condition are studied through three-dimensional finite element analysis.

Concentric winding has been widely used in small capacity AC motors due to its excellent performance. In this paper, a numerical calculation method based on the magnetic vector potential is proposed to calculate the stator end leakage reactance of concentric winding. In this case, the basic unit of numerical calculation becomes the coil group rather than the coil since concentric windings have different coil sizes. The calculated stator end leakage reactance of a prototype three-phase permanent magnet machine with concentric winding is validated using the finite element method. Compared to 3D electromagnetic field calculation, the proposed method does not require a complex modeling process and is therefore highly efficient computationally, requiring only a fraction of the calculation time.

In this paper, an improved motor is presented for a smart, vertical, multi-joint robot actuator. The motor design was optimized using methodologies such as the penalty function method (PFM) and response surface methodology. To improve its performance, different pole-slot combinations were applied considering its electrical and mechanical characteristics. Using 2D finite element analysis, results were compared from a previous model and a newly proposed model. The experimental results confirmed that the proposed model achieved improved performance at the rated point.