The physicochemical properties of La_0.8Ca_0.2Mn_1−xCo_xO₃ nanopowders as a function of Co content (x) have been investigated. La_0.8Ca_0.2Mn_1−xCo_xO₃ nanopowders were synthesized by sol-gel method and morphologically and structurally well characterized by Scanning electron microscopic (SEM), Infrared spectroscopic (IR) and Raman spectroscopic techniques. IR spectra shows peak at around 600 cm⁻¹ attributed to the stretching mode of MnO₆ octahedral and peak at 700 cm⁻¹ assigned to La-Ca-O-Mn bending vibrations. Raman spectra indicate peaks at around 512 and 652 cm⁻¹ related to the Jahn-Teller octahedral distortions. The intensity of these peaks increases with increasing Co doping. The UV-visible spectra were measured in the frequency range of 200-800 nm and two energy gaps were found at 1.63 eV and 3.294 eV for x = 0, 0.1 and 0.3.

Polycrystalline Ni_xFe_3-xO₄ thin films prepared by using a sol-gel process exhibited phase-pure spinel structure for the Ni composition up to x = 1.0. X-ray photoemission spectroscopy (XPS) and Raman spectroscopy investigations revealed that Ni ions mostly have valence of +2 and occupy the octahedral sites of the cationic sublattice. The Ni_xFe_3-xO₄ films exhibited higher electrical resistivity than that of Fe₃O₄ below 300 K. The increase in the resistivity is primarily ascribed to decrease in Fe²⁺-Fe³⁺ polaronic hopping rate in the octahedral sites due to the increase in the octahedral Ni²⁺ population.

In this study, we have systematically calculated the dynamic susceptibility spectra of LSMO (La_0.7Sr_0.3MnO₃) ferromagnetic nanopillars by means of a micromagnetic simulation. Simulation has been carried out for LSMO nanopillars consisted of disk and square shapes with respect to the height variation. The diameter of disk pillar and the length of square pillar were fixed to be 50 nm and the height of pillar were varied from 100 to 500 nm with increment of 50 nm. The exponential type magnetic pulses have been applied in the long axis and perpendicular to the initial spin configuration of the pillars. The dynamic susceptibility spectra of the pillar were determined by fast Fourier transform (FFT) based on the magnetization response. We have obtained the resonance frequency of the pillars from the imaginary part of the dynamic susceptibility spectra. Interestingly, the resonance frequency peak of the nanopillars increased as the height increased and followed the Kittel’s resonance formula. It was found that the demagnetization energy from dipolar interaction mainly contributed to the frequency resonance of the nanopillars.

Inductance is one of the most important components in order to make energy conversion in the power converters. The dynamics of power converter are affected by inductance. Therefore, in order to obtain accurate power converter dynamic model, one needs to have accurate inductance model. An inductance value is not always constant as it depends on current. Especially in the saturation region, inductance value decreases when current increases. On the other hand, exact eddy current and hysteresis losses estimation can be obtained with an accurate inductance model. This paper proposes an improved analytical inductance model that considers nonlinear B-H curve of a core material. A nonlinear B-H function is fitted using the Matlab Curve Fitting Toolbox. This function includes magnetic flux density (B) against magnetic field strength (H) variation in the both linear and saturation regions. The magnetic circuit model is obtained using a lumped parameter method and the Lambert W function is used to solve the equation which includes nonlinear core reluctance. In conclusion, a nonlinear analytical inductance model is proposed.

A birdcage coil integrated with a 16-channel, inductively coupled, radio-frequency (RF) array was designed to improve the magnetic-flux distribution for human brain magnetic resonance imaging at 7-T. A numerical calculation was performed using the finite-difference time-domain method for the birdcage coil with an inductively coupled array. The electromagnetic calculation results for the birdcage coil with the inductively coupled array were compared to those for the birdcage coil without an inductively coupled array in terms of their magnetic- flux, electric-field, and specific-absorption-rate distributions in a cylindrical phantom and human model. The proposed birdcage coil with an inductively coupled array offers a superior magnetic-flux sensitivity without sacrificing the RF power deposition at 7-T. The modifications of the coil geometry accompanying the inductively coupled RF array could be applied to the generally used transmit/receive volume coils and extended to parallel RF transmission array in ultra-high-field magnetic resonance imaging.

The half-metallicity and magnetism at the (001) surface of half-Heusler-structured YCrSb and YMnSb were investigated using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation. Both YSb-terminated surfaces and Cr- or Mn-terminated surfaces were considered for YCrSb and YMnSb. From the calculated local density of states and the total magnetic moments of the systems, the half-metallicity of the YSb-terminated (001) surface for YCrSb was preserved, whereas the surface for YMnSb was almost half-metallic. In contrast, the half-metallicity was destroyed at the Cr- or Mn-terminated surface of YCrSb or YMnSb. The magnetic moments of the Cr and Mn atom at the (001) surface were increased by 28 % and 15 %, respectively, compared to the bulk values due to band narrowing and increased exchange splitting at the surface.

Aerobic exercise is effective for preventing cerebrovascular diseases. In that, this study focuses on investigating cerebrovascular changes with MRA (Magnetic Resonance Angiography) images by comparing before and after the aerobic activity. As a result, acquired MRA images indicate that signal intensity is increased in case of ECA (External Carotid Artery), STA (Superficial Temporal Artery) with relation to comparing before-after aerobic activities. However, ICA (Internal Carotid Artery), VA (Vertebral Artery), BA (Vertebral Artery) decreased. The comparison of vessel thickness before-after exercising aerobics results in the rise of ECA, STA, while ICA, and VA, BA decreased. Cerebrovascular transformation during aerobic exercises is analyzed with MRA image. Such data show the changes of both blood flow volume and vessel thickness after aerobic activities. As the study demonstrates, aerobic exercises increase cerebral blood flow and vessel thickness. Therefore, aerobic exercises are expected to help preventing cerebrovascular diseases.

Leakage permeance of a permanent magnet (PM) is an important factor for improving the accuracy of electromagnetic device calculations based on a magnetic equivalent circuit (MEC). For PM leakage permeance calculations, the traditional simulation method of finite element analysis (FEA) and the lumped parameter analytical method (LPAM) have been considered; it was found that FEA has the disadvantage of a long calculation time and LPAM has low accuracy. The magnetic field lines distribution analytical method (MFLD) is proposed in this paper in order to raise computational efficiency and keep accuracy within a certain range. The electromagnetic features of open circuit fan-shaped PMs are presented by MFLD and finite element analysis (FEA) is adopted to match the MFLD results. In order to verify the validity of the proposed method in a magnetic system, the working points of PMs in an electromagnetic actuator are calculated, and the numerical results compared with the experimental results.

Cobalt ferrite nanoparticles (CoFe₂O₄) and cobalt zinc ferrites with general formula Co_xZn_1-xFe₂O₄ (x = 0.5, 0.6, 0.7) were prepared by sol-gel method at a low temperature with a final pH value of 7. Synthesized spinel ferrites were sintered at various temperatures (220, 400, 600, 800 and 1000℃). X-ray diffraction (XRD) was used to characterize the sizes of particles and structural properties. The average crystalline size of the prepared ferrite was ranged between 18-49 nm. The FTIR spectra however showed two strong absorption bands ranged between (1037.45-399.26 cm^-1), which is a spinel ferrite. The study also focused on several dielectric properties of the samples such as dielectric constant (ε'), dielectric loss tangent (tan δ) and complex dielectric constant (ε''). The variation of dielectric parameters (ε) and tanδ with frequency revealed that the dispersion was due to Maxwell-Wagner. Magnetization measurements showed that the coactivity (H_c), saturation magnetization (M_s), remanent magnetization (M_r) and squarenessremnance ratio (R = M_r/M_s) strongly depend on content of zinc.

Due to the high efficiency, high force capability and low cost, the linear permanent-magnet (PM) vernier (LPMV) machine is very suitable for long stroke applications such as urban rail transits. This paper proposes the LPMV machines with various topologies of half Halbach PM array, and investigates their electromagnetic performances, such as back electromotive force, force capability, PM eddy current loss and iron loss. Firstly, the configuration and operation principle of the LPMV machines are presented. By using the finite element method, it can be known that the LPMV machine with half Halbach PM array in the armature core exhibits high thrust and low detent force. Then, the demagnetizations of half PM array are analyzed to guarantee the security and credibility of the machine in operation. Finally, the effectiveness of the theoretical analysis is validated by the experiments on a prototype of the LPMV machine.

This study proposes an unequal air-gap model for PMSMs with the objective of reducing the torque ripple and improving the demagnetization characteristics. Shape optimization is performed to optimize the design variables of the unequal air-gap model, which are the shape of the unequal air-gap and the angle between the V-shaped permanent magnets. An optimization process was performed by the Kriging model based on Latin Hypercube Sampling (LHS), and Genetic Algorithm (GA). Finite element analysis (FEA) was also utilized to analyze the torque and demagnetization characteristics. As optimal design results, the torque ripple of the optimal model was reduced by 7.7 % and the demagnetization temperature was improved by 2.2 %.

This paper presents an optimization design and experiment of a high speed motor (HSM) for underwater thrusting systems by using magnetic flux density distribution (MFDD) of the stator, based on finite element analysis (FEA). The MFDD in the HSM is closely related to the electro-magnetic loss. This is an important factor when considering increasing efficiency, miniaturization, and reducing overall weight. To this end, a volumetric design of the rotor, which directly affects the magnetic flux density (MFD), was carried out using torque per rotor volume and a design line of electro-motive force. Calculation of the MFDD of the stator was derived from the area of the triangular element by the 2-D finite element method using the element node and the center of gravity. The flux density inside the element was derived by FEA. The maximum density distribution (MDD) and average density distribution (ADD) of the MFDD for the variable area (yoke, tooth, and shoe) of the stator core are presented. Efficiency optimization was performed by calculating the iron loss and efficiency reduction ratio using the ADD. On the basis of the manufactured 2.5 [kW] HSM, the optimal design of the MFDD was verified by comparing the FEA results with the experimental results at the rated operating point.

This paper deals with the design of an electromagnetic energy harvesting generator for the suspension system of a sport utility vehicle. The proposed generator is composed of a single coreless type permanent magnet layer, which increases flux density across the coil windings and eliminates flux leakage by using the Halbach PM array, thus improving the machine’s performance, including flux linkage and output power. The goal of the system is to regenerate energy from the kinetic energy of the suspension system of the sport utility vehicle. The proposed generator physically combines electrical and mechanical components, in which permanent magnets, coil windings, and back iron are attached to the body of the shock absorber. The design’s performance was investigated using the finite element method (FEM) and validated by comparison with experimental data.

The effects of Fe doping on structural, magnetic and magnetocaloric properties of La_0.94Bi_0.06Mn_1-xFe_xO₃ (x = 0, 0.05, 0.075, 0.1) compounds were investigated. X-ray analyses showed that the substitution of Mn by Fe produced no major structural change. It was found that the saturation magnetization, Curie temperature and maximum value of magnetic entropy change decrease with increasing Fe content. The decrease in magnetic entropy change was attributed to the decrease in saturation magnetization and the nature of phase transition transforms from first-order to second-order. The refrigeration capacities were determined to be 259 and 230 J/kg for the x = 0 and 0.075 samples, respectively at a field change of 5 T.

We investigate the effect of Nd doping on the magnetic and dielectric properties of nickel-cobalt ferrite. The samples were synthesized by sol-gel method and structural phase was determined by powder X-ray diffraction technique. X-ray diffraction studies reveal that the cubic spinel structure with space group Fd-3m is maintained for all the compositions. Doping with Nd atoms modified both the magnetic and dielectric properties of nickel-cobalt ferrite. A decrease in saturation magnetization and effective magnetic moment per atomic site is observed with increase in neodymium concentration. The doping of Nd into the Ni-Co ferrite lattice results in enhancement of coercivity and reduction of Curie temperature. The dielectric studies showed an increase in dielectric constant and decrease in loss tangent with the increase in Nd concentration. The frequency dependent dielectric measurements at room temperature were observed to obey the modified Debye model with a relaxation time of the order of 10^-4 s and spreading factor in the range 0.47-0.69. The observed resonance relaxation peaks shift towards lower temperature with increase in Nd concentration.

This paper proposes a novel hybrid suspension electromagnet for application in the middle-low speed maglev train. Its configuration and working principle are introduced. Mathematical models of the suspension force and guidance force are established accurately by equivalent magnetic circuit method (EMCM), from which the relationships of suspension force-control current-suspension gap and guidance force-guidance displacement are derived. Finite element method (FEM) is also applied to analyze the performances and characteristics of the novel hybrid suspension electromagnet. The analysis results are in good agreement with those calculated by EMCM, which is helpful in designing and optimizing the suspension system. The comparisons are made between the performances of the novel and the traditional electromagnets. The contrast results indicate that the proposed hybrid suspension electromagnet possesses better performances compared to the traditional structure, especially the little control current and the low suspension power loss.

The target of the current study is to inspect theoretically two-dimensional boundary layer flow of a Maxwell ferromagnetic fluid toward a flat plate. An external magnetic field due to two equal line dipole which are equidistant from the wall and perpendicular to the flow plane is applied. Cattaneo-Christov heat flux model is utilized in modified form of Fourier’s Law to disclose the heat transfer characteristic. Governing flow problem is normalized into ordinary differential equation by adopting similarity transform procedure. The solution of resulting non-linear ODE’s are solved by shooting technique based on Runge-Kutta algorithm with the help of MATLAB. Characteristic of sundry parameter like magneto-thermomechanical (ferrohydrodynamic) interaction parameter, dimensionless thermal relaxation, Prandtl number and Debora number on velocity and temperature profile are displayed via graphs and in tabular form. It is also pointed out that temperature profile suppresses by varying values of the thermal relaxation time and Prandtl number and increasing behaviour is seen against ferrohydrodynamic interaction. Present numerical results are compared with those published previously in the literature for the case of Newtonian fluid (α₁ → 0) and found an excellent agreement.

Magic angle spinning (MAS) nuclear magnetic resonance (NMR) for ¹⁹F and ¹H nuclei was used how exposure to high-pressure (70 MPa) H₂ gas affected an O-ring material. ¹⁹F MAS NMR revealed that poly(vinylidenefluoride-co-hexafluoroprophylene) in VDF/HFP = 76.1/23.9 mol % (FKM type 1) was involved in the O-ring material. This copolymer may undergo main-chain scission and termination to -CF₂H end groups during depressurization of high-pressure H₂. Evidence for formation of additional -CF₂H end group includes a small increase in the ¹⁹F MAS NMR signal at -96 ppm, and a corresponding ¹H MAS NMR signal at 7.1 ppm in comparison with those in the material that had not been exposed to high-pressure H₂. Neither the ¹⁹F nor the ¹H MAS NMR showed chemical shift after exposure to H₂; this absence of response means that exposure to H₂ did not affect the structure of the polymer.

The magnetic gradiometer onboard a maneuverable vehicle is subjected to not only magnetometer errors and misalignment errors but also magnetic interference of vehicle. Measurement precision of the magnetic gradiometer is greatly affected by those errors, so an integrated error calibration method is proposed in this paper. Firstly, considering vector magnetometer errors and magnetic interference, an integrated error calibration model for vector magnetometer is established, and ellipsoid fitting parameters are calculated by the least square algorithm under ellipsoid restriction, then the error calibration matrices are solved by the Cholesky factorization. Secondly, the misalignment error calibration matrices are obtained by solving the Orthogonal Procrustes problem. Finally, simulations and experiments with a cross magnetic gradiometer are performed to verify effectiveness and robustness of the proposed method. Results show that the proposed method can effectively calibrate the cross magnetic gradiometer, and measurement accuracy of the cross magnetic gradiometer is increased greatly.

As known, the variation of distances between the adjacent coils will affect the transfer efficiency in magnetic coupled resonance system. In order to explore the influence of distance on the optimum transfer efficiency, a four-coil magnetic coupled resonance system is established. Based on the mutual inductance coupling theory, the relationship between the transfer efficiency and coupling coefficient is obtained. Supported by the simulation analysis and experimental evidences, it is found that the coupling coefficient k₂₃ (between transmitter and receiver coils) is the most significant factor affecting the transfer efficiency. Under the optimal k₂₃, the transfer efficiency will increase with the coupling coefficient k₁₂ (between driver and transmitter coils). Besides, it will firstly increase and then decrease with the coupling coefficient k₃₄ (between receiver and load coils). Moreover, the theoretical calculation formula of k₂₃ is deduced, which can make a contribution to the optimization of parameters and improvement of transfer efficiency for the four-coil magnetic coupled resonance system.

The impedance matching problem of magnetic coupled resonant wireless power transfer system based on planar spiral coils is studied in this paper. Taken the coupling factors into account, the relationships between impedance matching, resonant frequency and transfer distance are analyzed. Supported by the simulation analyses and experimental evidences, it is indicated that the optimum matching resistances for transfer power and transfer efficiency are different. In details, the optimal matching resistance for output power decreases with the transfer distance, while that for the transfer efficiency does not vary with transfer distance. Thus, this research provides a valuable reference for the further research on adaptive impedance matching of magnetic coupled resonant wireless power transfer system.

Cerebrovascular disease is the critical cause of death and is important cause of disability worldwide and the leading contributor to the chronic disease burden. Cerebrovascular disease, is also the leading contributor, to the chronic disease burden. In this study, we analyzed the factors affecting MRI, which are critical for the diagnosis of cerebrovascular disease, with high mortality rate, and high medical burden. In the present study, data from the Korean National Hospital Discharge In-depth Injury Survey for three years, from 2012 to 2014, we used. The subjects were 14,383 patients with cerebrovascular disease over 20 years of age who were first diagnosed with the international disease classification code I60-I67: cerebral hemorrhage, cerebral infarction, obstruction and stenosis of the precerebral artery, cerebral aneurysm etc. The analysis revealed the independent variables affecting MRI examination of cerebrovascular diseases were sex, age, type of insurance, admission route, length of stay, treatment result, location of hospital, and the number of hospital beds.

In the present study, a pad was developed using acetic acid in an attempt to verifiably decrease the metal- artifact presence in human subjects. The subjects of this study are 20 patients who underwent neck magnetic resonance imaging (MRI) examinations between January 2016 and December 2016. The subject ages are between 30 yr and 62 yr. First, a pad was prepared using acetic acid and a solution comprising a thickening agent and glycerin (ultrasound gel). The prepared acetic-acid gel pad was attached to the periphery of the implant and subjected to MRI. The test was carried out 20 times before and after the use of the acetic-acid gel pad. The obtained signal-to-noise ratios (SNRs) were compared in the region of interest (ROI) before and after the use of the 12 pads. As a result, the SNR was increased after the pad usage. As a result, the metal artifacts were decreased after the use of the pad. The developed pad can be used in the future as a tool for the reduction of the MRI metal artifacts.

The purpose of this study was to investigate the effect of rTMS on upper limb dysfunction and hemineglect patients after stroke and to find out the most effective application method. This study was conducted with 25 subjects who were diagnosed as a hemiparesis by stroke. Participants in the experimental (12 members) and control groups (13 members) received rTMS and sham rTMS during a 20 minutes session, five days per week for four weeks, respectively, followed by task-oriented training during a 30 minutes session. Motor recovery evaluation was performed by fugl meyer assessment (FMA), box and block test (BBT), albert test (AT) and grip strength test. The experimental group showed significant increments in FMA, BBT, AT, and grip strength test, compared to the pre-intervention results (p < 0.01). Furthermore, the control group showed significant increments in the FMA, BBT, AT, compared to the pre-intervention results (p < 0.05). A significant difference in the post-training gains in FMA, AT, and grip strength test were observed between the experimental group and the control group (p < 0.05). In addition, the effect size for gains in the experimental and control groups was very strong in FMA, AT, grip strength test (effect size = 1.29, 1.45, 0.96 respectively) and the effect size for gains in the experimental and control groups was very weak in BBT (effect size = 0.20). The findings demonstrate that application of 1 Hz rTMS combined with task-oriented training can be helpful in improving upper limb function and hemineglect of stroke .

Rotator cuff disease occurs in adults is very common cause of shoulder pain causes is known as one of the. Combined oblique coronal and oblique sagittal standard magnetic resonance (MR) imaging is highly accurate for detecting full-thickness rotator cuff tears. However, the accuracy of standard MR imaging is lower for partial- thickness tears. Small rotator cuff tears can be obscured by partial volume effect if the imaging planes are not orthogonal to the surface of the cuff. Angling the oblique sagittal images perpendicular to the lateral 2 or 3 cm of the supraspinatus tendon would reduce the partial volume effect, and might make tears in this region more conspicuous. The purpose of our study was to compare the accuracy for diagnosing rotator cuff tears of oblique coronal images supplemented with standard oblique sagittal images versus thinner-section modified oblique sagittal fat suppressed fast spin-echo T2-weighted images. For full-thickness supraspinatus tendon tears, our study confirms that oblique coronal and standard oblique sagittal images are very accurate for diagnosing tears, and that supplementing oblique coronal images with thinner-section angled oblique sagittal images does not improve diagnostic accuracy for those few full-thickness tears that are missed on standard MR images. In conclusion, there was a slight improvement in accuracy for diagnosing rotator cuff tears, particularly partial-thickness tears, for the staff radiologist using the thinner-section angled oblique sagittal images.

Nonlinear mathematical problems and their solutions are of great importance in solitary waves. In soliton theory, an efficient tool to attain various type of soliton solutions is the Exp-function technique. This paper aims at finding soliton wave solutions of a viscous incompressible fluid through convergent or divergent channel in the existence of a magnetic field. By an appropriate use of local similarity transformation we obtained an ordinary differential equation. It is solved by Exp-function technique. It is observed that under discussion technique is user friendly that requires minimum computational work. Also we can extend it for physical problems of different nature as well.