Bentonite is a kind of crystalline clay mineral with the major constituent of montmorillonite. Bentonite mines should be investigated in different areas with different climatic and environmental conditions. Kerman, is a province in the southeast of Iran famous for its rich resources of bentonite mines. In the present study, the physical and chemical characteristics of the supplied bentonites from three different mines of Kerman (Kheirabad, Tang-e Quchan and Horjand) were investigated. Kheirabad sodium bentonite sample was selected as a potent adsorbent of organic and inorganic pollutants due to high swelling index. Besides, magnetite nano composites were synthesized by stabilizing Fe₃O₄ nanoparticles on desired bentonite. The properties of nanocomposites were studied using FTIR, XRD, VSM, BET and TEM analyses.

In this paper, it is proposed to adopt Pulsed Eddy Current (PEC) testing of coaxial double coil structure to implement the detection on residual wall thickness of pipeline corrosion in oil and gas gathering and transportation station, in the view of reduction of wall thickness caused by corrosion. The electromagnetic field theory is applied to conduct theoretical analysis on PEC detection. On such basis, a theoretical model of coaxial double coil structure for PEC detection is built, and the relation of voltage phase of the detected signal varying with the wall thickness of the pipeline is derived. Then a method for evaluating the residual wall thickness of pipelines based on the phase trough time of PEC signals is proposed. Moreover, the parameters of the PEC probe are optimized by finite element method, and the detection system is designed accordingly. As a result, the practicability of the detection system and the correctness of the theoretical model are verified by experiments, proved that the model can realize the detection of the residua wall thickness under the condition of different media transported by the pipeline.

Lift-off is considered as one of the most critical parameters that poses a major challenge in the appropriate application of magnetic flux leakage inspection technique. Sediments and welds are presented in the internal of all pipelines and cause lift-off. This paper investigates the influence of lift-off distances on the components of the three-axis MFL technique and, therefore, the lift-off effect on the corrosion detection sensitivity. COMSOL software is used to set up the 3D FEM modeling of three-axis MFL technique. In order to simulate internal pitting corrosion of oil and gas pipelines, two adjacent pits of different depths are modeled on the surface of a carbon steel plate. At a range of lift-off values, MFL responses from this defect geometry are computed and the relationships between the lift-off distances and obtained MFL signals are analyzed in detail. Finally, the validity of the simulation results is verified by experimental tests.

This paper presents an improved 2-D analytical model to predict the magnetic field distributions and torque characteristics for a flux focusing disk-type permanent magnet eddy current coupling. Due to the inhomogeneous physical properties in the permanent magnet regions, based on the equivalent magnetic circuit method, a fictitious magnetization for the iron cores is introduced to simplify the complexity of modeling. The magnetic flux density distributions are derived when the eddy current generated in the copper plate and its back iron is reasonably concerned in 2-D Cartesian coordinates. Then, the explicit expression of torque is given and the torque-speed characteristics are analyzed. In the end, the calculated results of the proposed model are compared with those obtained from the magnetic equivalent circuit model and 3-D finite-element simulations.

To improve the efficiency of the liquid metal magnetohydrodynamic (LMMHD) generator, a new type of magnet structure of LMMHD system is designed in paper. The internal magnetic gathering capability is enhanced by imitating the arrangement of the Halbach array magnet. The magnetic induction intensity of conventional magnetic channel, Halbach magnet channel, and the new type of magnet channel, which is derived from basic Halbach are compared via ANSYS Maxwell 2D model. Simulation results show that Halbach magnets have better capacity of magnetism gathering and are more efficient at gathering electricity than conventional methods. The new type of magnetic has advantages of small size, low cost, high induction intensity, high output voltage and high power.

In blood, the concentration of red blood cells varies with the arterial diameter. In the case of narrow arteries, red blood cells concentrate around the centre of the artery and there exists a cell-free plasma layer near the arterial wall due to Fahraeus-Lindqvist effect. Due to non-uniformity of the fluid in the narrow arteries, it is preferable to consider the two-phase model of the blood flow. The present article analyzes the heat transfer effects on the two-phase model of the unsteady blood flow when it flows through the stenosed artery under an external pressure gradient. The direction of the artery is assumed to be vertical and the magnetic field is applied along the radial direction of the artery. Blood is considered as a non-Newtonian Casson fluid with uniformly distributed magnetic particles. Both the blood and magnetic particles are moving with distinct velocities. This two-phase problem is modelled using the Caputo-Fabrizio derivative approach and then solved for an exact solution using joint Laplace & Hankel transforms. Effects of pertinent parameters such as Grashoff number, Prandtl number, Casson fluid parameter and fractional parameters, and magnetic field on blood velocity and particle velocity have been shown graphically for both large and small values of time. Both velocity profiles increase with the increase of Grashoff number and Casson fluid parameter and reduce with the increase of magnetic field and Prandtl number. The behaviour of temperature is studied for different values of the fractional parameter.

This work presents the use of combinations between a wireless radio-frequency surface coil and a wireless 16-leg birdcage coil that are inductively coupled to improve the magnetic field sensitivity and uniformity. A single surface loop coil operating as transmission/reception (Tx/Rx) coil was designed for mouse head imaging at a magnetic field strength of 9.4-T. Numerical analyses using finite-difference time-domain were performed to compute the sensitivity and homogeneity of magnetic and electric flux density fields for each of the coil combinations. Maximum field values and standard deviation were used as statistical parameters to compare the sensitivity and homogeneity of the fields produced by the Tx/Rx surface coil for each case, when the wireless inductively coupled coils were used. The electromagnetic analyses were applied to a cylindrical oil-based phantom and a mouse model. The proposed combinations of the surface coil with the inductively coupled wireless surface and wireless volume coils offer an enhanced magnetic-flux sensitivity and RF excitation field distribution at 9.4-T. The modifications to the surface coil geometry by adding the inductively coupled radio-frequency coil combinations could be applied to the generally used transmit/receive surface coils and extended to parallel radio-frequency transmission array at ultra-high-field magnetic resonance imaging.

We theoretically and numerically investigate ferrimagnetic domain wall motion driven by damping-like spinorbit torque. We find that the damping-like spin-orbit torque combined with the interfacial Dzyaloshinskii-Moriya interaction efficiently drives the ferrimagnetic domain wall especially at the angular momentum compensation point. We obtain the analytic expression of the domain wall velocity with respect to the current density and the net spin density, which is in agreement with numerical simulation. The analytic expression is applicable to arbitrary compensation conditions, ranging from the ferromagnetic limit to the antiferromagnetic limit, and is thus useful to design and interpret ferrimagnetic domain wall experiments at various temperatures or compositions.

The purpose of this study was to compare the difference in peak velocity (PV) and average flow (AF) values between the shimming of the aortic arch (AA) and the left ventricle (LV) using the 2D phase contrast (PC) technique at 1.5 Tesla and 3.0 Tesla. The sino-tubular junction (S-T junction), the proximal AA, and the LV, an aortic valve, were examined using a 2D PC technique at 1.5 Tesla and 3.0 Tesla. At 1.5 Tesla and 3.0 Tesla, 2D PC technique was used to examine the proximal AA Sino-Tubular (S-T) junction and LV was examined at the aortic valve area. shim was not used (no_Shim) in 1.5 Tesla and 3.0 Tesla to compare differences in heart blood flow due to magnetic field strength. To assess the difference due to shimming, an auto_shim, target_shim was used and an all_shimthat used auto and target shim simultaneously was used. The average value between 1.5 Tesla and 3.0 Tesla as a result of inspection was different when AA_AF was no_shim and all_shim. In LV_AF, the difference in mean values was found in 1.5 Tesla and 3.0 Tesla when it was no_shim and all_shim. Other tests did not show any significant differences. Also, according to the shimming method in 1.5 Tesla, the mean value difference occurred in AA_AF and the mean value difference in LV_AF in 3.0 Tesla. In conclusion, it is necessary to improve uniformity of magnetic field through shimming for accurate blood flow evaluation in 1.5 Tesla and 3.0 Tesla. Therefore, this study is expected to be used as a basis for improving the uniformity of magnetic field.

In this paper, a high resolution magnetic measurements are performed in an AES (advanced encryption standard) cryptographic FPGA by using a newly designed magnetic probe. The probe consists of high resolution scanning system and magnetic field collecting coil integrated with 3-stage low noise amplifier to enhance the sensed voltage. Also, to improve the performance of the magnetic coil, the Si-substrate is removed under the coil by using FIB process. The results and discussion section clearly shows that, the proposed magnetic probe gives more detailed information about the susceptible area of an AES cryptographic FPGA surface with high resolution maps in different frequency bands compared with the existing magnetic probe.

K₂SnCl₆ single crystals doped with Cu were grown by the evaporation of saturated solution. The electron magnetic resonance (EMR) of the Cu²⁺ ion in the crystal has been investigated by using an X-band spectrometer. The rotation pattern in the crystallographic plane together with spin Hamiltonian parameters of Cu²⁺ ion in K₂SnCl₆:Cu single crystal shows that the local site symmetry of the Cu²⁺ ion is cubic at room temperature. The calculated spectroscopic splitting factor g of Cu²⁺ impurity ion is 2.1908(±0.0007). The hyperfine constants of Cu²⁺ impurity ion due to the ⁶³Cu and ⁶⁵Cu isotopes in K₂SnCl₆:Cu crystal are 0.83(±0.01)×10⁻⁴ cm⁻¹ and 0.89(±0.01)×10⁻⁴ cm⁻¹, respectively. It turns out that the Cu²⁺ ion substitutes for the K⁺ ion without any nearby charge compensation.

Fractional-slot concentrated windings (FSCWs) are characterized with many advantages. However, their magnetic fields have rich space harmonics. These harmonics, especially tooth harmonics, have negative effect on machine performances. This paper proposes a new method to reduce the tooth harmonics in FSCW permanent-magnet (PM) machine, in which the magnetic distribution in air-gap will be affected by winding span radian. Also, a new stator structure is designed on the method. By using the new stator design, each order tooth harmonic can be reduced significantly and the working harmonic can also be increased slightly. Simultaneously, the unbalanced radial magnetic force can be significantly weakened. The basic principle of tooth harmonic reduction method can be analyzed by using the stator structure of the FSCW machine with single layer windings. Then, a three phase 18-slot/16-pole FSCW machine with double layer windings is newly designed, which can effectively weaken the tooth harmonic components of FSCW machines. It is shown that, under the fixed electrical and geometrical constrains, the designed FSCW machine has better performances, such as loss, vibration and noise, than the conventional ones.

The article presents the results of the experimental implementation of separate and opposing linear structures of different sizes using NdFeB permanent magnets. It focuses on the distribution of the resulting magnetic induction. For both separate and opposing structures, composed of two layers of magnets, the magnetic induction attained was much more affected by changes in the width of the central magnet than by the increasing width of side magnets. When the width of the central magnet in either of the two opposing double-layer Halbach structures was increased approximately three times, the area of the uniform magnetic field attained in the middle of a 20-mm-wide air gap was roughly three times bigger with only ca 7% lower induction in comparison with opposing Halbach structures of optimized dimensions. These make it possible to generate the maximum magnetic field in the middle of the air gap, but only in a narrow band.

This paper deals with the characteristic analysis of permanent magnet (PM) wind power generators according to stator winding topology to compare the machine performance, and the experimentally measured current with grid connection is employed for the investigation. The analysis models dealt with in this study have the slotless structure in their stator core to eliminate the cogging torque with the identical PM rotor, and three coil winding types according to coil pitch and winding types are addressed for their comparison. One of the analysis models is manufactured to be integrated with a grid-connected power converter, and the measured phase current of the generator is applied to investigate their flux density, resulting radial force and power loss characteristics of each analysis model. For the reasonable comparison, the generators have very similar equivalent circuit parameters, such as induced voltage and resistance, so the load voltage and current characteristics are almost identical. From the results dealt with in this study, one of the analysis models is proposed to be applied for the small-scale wind power generation systems.

Most studies on non-rare-earth motors focus on the inner-rotor-type motors, and little research has been conducted on the outer-rotor-type motors. This paper suggests a novel outer rotor fan-type permanent magnet synchronous motor (PMSM) as a non-rare earth outer rotor motor. To verify the superiority of the efficiency and output power, the novel outer rotor fan-type PMSM is compared with the surface permanent magnet synchronous motor (SPMSM), which is primarily used as an outer-rotor-type motor. The detailed design and characteristics of the outer rotor fan-type PMSM was also studied. Finally, the output characteristics of the outer rotor fan-type PMSM were verified through prototyping.

Magnetic saturation and complex stator structure of Switched Flux Permanent Magnet Machine (SFPMM) compels designers to adopt universally accepted numerical method of analysis i.e. Finite Element Analysis (FEA). FEA is not preferred for initial design due to its computational complexity and is time consuming process because of repeated iterations. This paper presents an accurate analytical approach for initial design of proposed twelve-stator-slot and ten-rotor-tooth (12/10) with trapezoidal slot structure SFPMM. Air-gap Magnetic Equivalent Circuit (MEC) models with Global Reluctance Network (GRN) methodology is utilized for calculation of open-circuit flux linkage. Fourier Analysis (FA) for cogging torque, and Maxwell Stress Tensor (MST) method for electromagnetic torque where radial and tangential components of the air-gap flux density are produced by the currents flowing in three phase armature winding. Analytical predictions are validated by FEA utilizing JMAG software and shows errors less than ~2% for open-circuit flux linkage, ~4.2% for cogging torque, and ~2% for average electromagnetic torque.

This paper deals with the comparative investigation on the electromagnetic field characteristics of interior permanent magnet synchronous motors (IPMSMs) based on finite element method. With identical magnetic structure, this paper proposes newly designed PM magnetization patterns for the cogging torque reduction. Based on this method, in spite of the longer stack length of the rotor and stator core, the torque characteristics can be much more improved in comparison with the conventional model. Along with the torque characteristics, the performance evaluation is also addressed based on the analyzed power loss values.

Variation of intrinsic coercivity of the HDDR-treated Nd_12.5Fe_80.8B_6.4Ga_0.3 alloy after heating in various modes was investigated. Influence of vacuum degree and cooling after heating on the coercivity of the HDDR material was examined. The heat-treated HDDR material had consistently higher coercivity when it was quenched after heating compared to when slow-cooled. Higher coercivity in the quenched material was attributable to the grain boundary with lower Fe content. HDDR-treated material heated in high vacuum showed consistently higher coercivity than the material heated in lower vacuum, and this was attributed to less heavily oxidized surface. Reduced coercivity of the HDDR-treated material heated at moderate temperature was noticeably recovered at higher temperature, and this was attributed to lower Fe content in the grain boundary.

In this paper, we fabricated novel magnetostrictive composites by embedding <110>-oriented Tb-Dy-Ho-Fe fibers in an epoxy matrix. The magnetostrictive and magnetic properties (magnetostriction, magnetization, piezomagnetic coefficient and relative permeability) of the proposed composites were measured, analyzed, and compared to those of Tb_0.29Dy_0.48Ho_0.23Fe_1.9 alloy and Tb_0.3Dy_0.7Fe₂ continuous-fiber/epoxy composites. Tb_0.29Dy_0.48Ho_0.23Fe_1.9 continuous-fiber/epoxy composites have a saturation magnetostriction (λ_s) of 840 ppm and saturation magnetization (M_s) of 0.75 T. Their piezomagnetic coefficient exhibits a maximum value (8.2 μm/kA) at 19 kA/m. These proposed composites exhibit a large magnetostriction in high magnetic fields (> 400 kA/m) and a large relative permeability in low magnetic fields (< 100 kA/m). This result indicates that the given composites perform better than the Tb_0.29Dy_0.48Ho_0.23Fe_1.9 alloy and Tb_0.3Dy_0.7Fe₂ fiber/epoxy composites. Thus, the composites with characteristics of high sensitivity and large magnetostriction can be used in the field of ultrasonic sensing.

Magnetorheological (MR) transmission that uses the rheological effect of MR fluid to transfer power is a new form of power transfer, which can achieve stepless control of torque and speed by adjusting the intensity of external magnetic field. In the study, a water-cooling heat dissipation scheme was proposed. The temperature simulation of MR transmission under natural heat dissipation and water-cooling heat dissipation was carried out by using the finite element method. Based on the design of the water-cooling MR transmission device (MRTD), the torque transmission and temperature rise characteristics of the MRTD were studied, and the influence of the heat dissipation mode on the transmission torque of the device was explored. Results show that the water-cooling method can control the temperature rise of the MRTD effectively.

Magnetic fluid seals are widely used technical applications of magnetic fluid. This paper presents a numerical simulation model to obtain the boundary of magnetic fluid in seals. The magnetic field in the seal is solved by finite element method, and the boundary is calculated by using Navier-Stokes equations in magnetic fluid. In order to observe the surface and obtain the seal capacity, the plane magnetic fluid seal experiment is carried out. The relationship between the seal capacity and the magnetic fluid volume is presented. The seal capacity which is obtained by the theoretical analysis has well congruence with the result of the experiment. The displacement of boundary with the pressure difference is quantitatively depicted.

Due to some limitations of permanent-magnet (PM) production and magnetizing technology, it is difficult to construct the large magnetic poles of high-power surface-mounted PM machines by using integral magnets. One simple solving scheme is that the large magnetic poles can be formed by several parallelly magnetized magnet segments. For the surface-mounted PM machines with parallelly magnetized magnet segments, this paper gives an accurate analytical solution of the magnetic field. First, in 2-D polar coordinates, the PM machine model is divided into three subdomains, and the magnetic field governing equations are established in each region. By adopting the theory of Fourier’s series and the method of separating variables, the solutions of the magnetic field are determined according to associated boundary conditions. Then, the proposed analytical model is compared with finite element method, and the results show that they have a good agreement. Based on the obtained magnetic field solution, the induced electromotive force of a designed PM machine is calculated, and the result is verified by experiment.

In order to design a kind of high-sensitive, narrow-band and portable search coil magnetometer, based on the principle of magnetic measuring, an equivalent model of search coil magnetometer with parallel matched capacitor is established. The formula of the induced coil is derived, low-noise integrated operational amplifier is designed and made as the preamplifier circuit of search coil magnetometer. The parameters of the inductive coil based on multi-parameter joint optimization are obtained under consideration of the sensitivity, bandwidth, weight and volume of the inductive coil simultaneously. The search coil magnetometer test is completed in the electromagnetic shielding room. And the result shows that the sensitivity of the designed search coil magnetometer is under the precondition of guaranteeing the weight, volume and bandwidth, which is basically the same as that of the simulation.

The disaggregation and displacement of stacked red blood cell (RBC) are known to be dependent on the electric state of hemoglobin and the strength and gradient of external magnetic field. The present study has been investigated the dependence of the change in aggregation and mobility of RBCs on the intensity and time duration of pulsed magnetic field (PMF), in addition to stimulus area. The magnetic field intensities are 0.07, 0.19, and 0.27 T, pulse time of 0.102 ms and pulse repetition rate was 1 Hz. Live blood analysis was used in order to quantitatively estimate the mobility and morphology of RBC exposed to PMF stimulus. The optimal time and intensity of PMF stimulus were 10 minutes and 0.27 T. The difference in the stimulus area did not show much. The continuance of the effect of PMF stimulus was observed to be 2 hours. Also it was verified the movement of the RBCs was accelerated for steady exposure of PMF stimulus. In order to identify a link between disaggregation in rouleau-formed RBCs and PMF stimulus, it is necessary to investigate the correlation between PMF intensity and the stimulus time, the mobility of RBCs, and the number of stacked RBCs.

This article focuses the flow through non-Darcy porous medium. The flow is due to the squeezing phenomenon. The magneto viscous fluid is accounted. Formulation of the flow problem is interpreted the salient features of Ohmic heating (Joule heating), viscous dissipation and auto-catalyst and reactants (i.e. homogeneousheterogeneous reactions). A whole analysis is carried out with different diffusion coefficients for both auto-catalyst and reactants. It is also desired to observe the dependence of convective surface condition on flow regime in heat transport process. The resulting non-linear partial differential equations are found to be governing by dimensionless ordinary differential equations with the implementation of similarity solutions. A homotopic procedure based on an iterative scheme is utilized for the solutions of the flow problem. Flow velocity, fluid temperature and concentration are addressed via graphs for different values of geometrical and rheological parameters of considered flow problem. Moreover, skin friction co-efficient and Nusselt number are sketched and discussed graphically. The analysis reveals that higher values of mass diffusion ratio parameter result reduction in concentration of specie B whereas concentration of specie A enhances for higher mass diffusion ratio parameter.