MnBi_1-xTi_x (x = 0, 0.4, 0.7, 1) alloys were prepared by arc-melting, followed by heat treatment. X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) were used to measure and investigate the phase structure and magnetic properties. The temperature dependent magnetization curves indicate that the phase transitions between LTP and HTP MnBi occur with heating or cooling in MnBi_1-xTi_x (x ≤ 0.7) samples. However, MnTi samples are in Mn₂Ti single-phase, with very low magnetic properties. Furthermore, the coercivity exhibits a positive temperature coefficient. The results show that the optimal content of Ti for the coercivity of MnBi_1-xTi_x alloy is x = 0.4. For MnBi sample, the coercivity reaches a maximum value of 1.13 T at 550 K. However, the remanence and energy product show apparent decrease with the addition of Ti in MnBi_1-xTi_x alloys.

The effects of manganese substitution on the crystallographic and magnetic properties of Li-Zn-Cu ferrite, Li_0.5Zn_0.2Cu_0.4Mn_xFe_2.1-xO₄ (0.0 ≤ x ≤ 0.8), were investigated. Ferrites were synthesized via a conventional ceramic method. We confirmed the formation of crystallized particles using X-ray diffraction, field emission scanning electron microscopy and Mössbauer spectroscopy. All of the samples showed a single phase with a spinel structure, and the lattice constants linearly decreased as the substituted manganese content increased, and the particle size of the samples also somewhat decreased as the doped manganese content increased. All the Mössbauer spectra can be fitted with two Zeeman sextets, which are the typical spinel ferrite spectra of Fe³⁺ with A- and B-sites, and one doublet. The cation distribution was determined from the variation of the Mössbauer parameters and of the absorption area ratio. The magnetic behavior of the samples showed that an increase in manganese content led to a decrease in the saturation magnetization, whereas the coercivity was nearly constant throughout. The maximum saturation magnetization was 73.35 emu/g at x = 0.0 in Li_0.5Zn_0.2Cu_0.4Mn_xFe_2.1-xO₄.

This study investigates the dynamic magneto-mechanical behavior of magnetization-graded ferromagnetic materials Terfenol-D/FeCuNbSiB (MF). We measure the dynamic magneto-mechanical properties as a function of the DC bias magnetic field (H_dc). Our experimental results show that these dynamic magneto-mechanical properties are strongly dependent on the DC bias magnetic field. Furthermore, the dynamic strain coefficient, electromechanical resonance frequency, Young’s moduli, and mechanical quality factor of Terfenol-D/FeCuNbSiB are greater than those of Terfenol-D under a lower DC bias magnetic field. The dynamic strain coefficient increases by a factor of between one and three, under the same DC bias magnetic field. In particular, the dynamic strain coefficient of Terfenol-D/FeCuNbSiB at zero bias achieves 48.6 nm/A, which is about 3.05 times larger than that of Terfenol-D. These good performances indicate that magnetization-graded ferromagnetic materials show promise for application in magnetic sensors.

Significantly enhanced low-field magnetoresistance (LFMR) and maximum dMR/dH {(dMR/dH)_max} values were successfully achieved from La_0.7Sr_0.3MnO₃(LSMO)-manganese oxide composite samples prepared by liquid phase sintering, compared with those of the same composites prepared by solid state reaction. For this study, pure LSMO and LSMO-manganese oxide composites with various nominal compositions of (1-x)LSMO–xMn₂O₃ (x = 0.1, 0.2, 0.3, 0.4, and 0.8) were sintered at 1450℃, above the eutectic temperature of 1430℃, for 1 h in air. The highest LFMR value of 1.28% with the highest (dMR/dH)_max value of 21.1% kOe⁻¹ was obtained from the composite sample with x = 0.3 at 290 K in 500 Oe. This enhancement of LFMR and (dMR/dH)_max values is ascribed to efficient suppression of magnetic disorder at the LSMO grain boundary, by forming a characteristic LSMO-manganese eutectic structure.

We fabricated textured polycrystalline CoFe₂O₄ thin films on Pt(111)/TiO₂/SiO₂/Sisubstrate through a sol-gel method. We varied the thickness of the films, by using precursor solutions with different concentrations of 0.1, 0.2, and 0.3 M, and by depositing 5, 8, or 10 layers on the substrate by spin-coating. X-ray diffraction spectra indicated that when the precursor concentration of the solution was higher than 0.1 M, the spin-coated films were preferentially oriented in the 〈111〉 direction. Inspection of the surface morphology by scanning electron microscopy revealed that CoFe₂O₄ thin films prepared with 0.2 M solution and 5-time spin-coatings had smoother surface, as compared to the other conditions. Each coating had an average thickness of about 50 nm. The magnetic properties measured by vibrating sample magnetometer showed magnetic anisotropy, as evidenced from the difference in the in-plane and out-of-plane hysteresis loops, which we attributed to the textured orientation of the CoFe₂O₄ thin films.

Anisotropy coupling in thin films with mixed induced and shape anisotropies is investigated. A 200-nm-thick Co-Fe-Pd-B thin film with a large induced anisotropy of 57 Oe is fabricated and then patterned into micronsized cells to provide shape anisotropy, whose strength has a similar magnitude to that of the induced anisotropy for enhancing the anisotropy coupling. The angles between the two mixed anisotropies considered are 0°, 90°, and 110°. Hysteresis loops measured under in-plane magnetic fields along various directions indicate no anisotropy coupling behaviour for all the three angles examined in this study.

For heat-assisted magnetic recording, magnetization reversal probabilities of nano-Pt/MnSb multilayer film with perpendicular magnetic anisotropy under thermal pulse activation were investigated numerically by solving the Landau-Lifshift Gilbert Equation. Magnetic parameters of nano-Pt/MnSb multilayer were used with anisotropy energy of 3 × 10⁵ erg/cc and saturation magnetization of 2100 G, which offer more than 10 y data stability at room temperature. Scheme of driven magnetic field and thermal pulse on writing mechanism was designed closely to real experiment. This study found that the chosen material is potential to be used as a high density magnetic storage that requires low writing field less than two-hundreds Oersted through definite heating and cooling interval. The possibility of writing data with a zero driven magnetic field also became an important result. Further study is recommended on the thickness of media and thermal pulse design as the essential parameters of the reversal magnetization.

The objective of this study was to study the effect of magnetized water on porcine cumulus cell-oocyte complexes (COCs). Oocytes obtained from female pig were cultured in a medium magnetized at 0, 2000, 4000, and 6000 Gauss (G) for 5 minutes using the neodymium magnet. Subsequently, intracellular hydrogen peroxide (H₂O₂) concentration, glutathione (GSH) activity, oocyte membrane integrity, anti-apoptosis factor Bcl-xL expression, and nuclear maturation were analyzed. The intracellular H₂O₂ levels in COCs cultured for 44 hours were not significantly different among the variously magnetized samples. However, GSH activity were significantly higher in the magnetized samples compared to the 0 G sample. The Bcl-xL mRNA expression in COCs cultured for 44 hours was higher in the 4000 G sample than other treatment groups. Membrane damage in COCs cultured for 22 and 44 hours was significantly lower in 4000 G group than control group. On the other hand, nuclear stages as maturation indicator significantly increased in 2000, 4000, and 6000 G groups compared to 0 G group. These results indicate that incubation of porcine oocytes and cumulus cells in magnetized medium improves intracellular GSH levels, membrane integrity and nuclear maturation, and inhibits apoptosis in vitro.

The purpose of this study is to figure out how uptake counts of technetium (^99mTc) among radioisotopes in the human body are affected if computed tomography (CT), magnetic resonance imaging (MRI) and isotope examination are performed consecutively. ^99mTc isotope material, iodinated contrast media for CT and paramagnetic contrast media for magnetic resonance (MR) were used as experimental materials. First, ^99mTc was added to 4 cc normal saline in a test tube. Then, 2 cc of CT contrast media such as Iopamidol^® and Dotarem^® were diluted with 2 cc normal saline, and 2cc of MRI contrast media such as Primovist^® and Gadovist^® were diluted with 2 cc normal saline. Each distributed contrast media was a total of 4 cc and included 10m Ci of ^99mTc. A gamma camera, a LEHR (Low energy high resolution) collimator and a pin-hole collimator were used for image acquisition. Image acquisition was repeated a total of 6 times and 120 frames were obtained and uptake counts of ^99mTc were measured (from this procedure). In this study, as a result of measuring the uptake counts of ^99mTc using the LEHR collimator, the uptake counts were less measured in all contrast media than normal saline as a reference. In particular, the lowest uptake counts were measured when Gadovist^®, contrast media for MRI, was used. However, the result of measuring the uptake counts of ^99mTc using the pin-hole collimator showed higher uptake counts in all contrast media, except for Iopamidol^®, than normal saline as a reference. The highest uptake counts were measured particularly when Primovist^®, contrast media for MRI, was used. In performing the gamma camera examination using contrast media and ^99mTc, it is considered significant to check the changes in the uptake counts to improve various diagnosis values.

A portable clip-type pulsimeter equipped with a magnetic sensing Hall device has been developed to raise the accuracy of oriental disease diagnosis and therapy by convergence of magnetism and oriental medicine. To improve accuracy and reliability of conventional pulsimeter due to subjective analysis of the pulse wave and measuring position dependency of the arterial pulse sensor, the fuzzy algorithm was applied to analyze the strong- and weak-pulse wave symptom. Optimal time for electronic acupuncture was calculated using fuzzy rules and interference were drawn from objective data in view of pre-treatment. Moreover, the electrical characteristics of the pain parts that respond to acupuncture point were applied in view of post-treatment to propose the scientific pulse wave algorithm and simulation experiment.

Three-dimensional computed tomography is an effective tool to estimate the liver volume of living donors for the live liver transplantation. When additional operation is required, magnetic resonance imaging is conducted to determine the safety of the donor. This study compared the accuracy of magnetic resonance imaging and computed tomography in estimating 3D liver volume of 23 male and 7 female donors who underwent both magnetic resonance imaging and computed tomography tests before the transplantation. The analysis was conducted to see whether the liver’s estimated total volumes and the left lobe volumes obtained from 3Dmagnetic resonance imaging and 3D-computed tomography were identical. Volumes of the right lobe estimated with 3D-magnetic resonance imaging and 3D-computed tomography were compared with the actual volume of the right lobe harvested in the operating room because the volume of the right lobe is an important determinant in the safety of the donor. The total volume of the liver estimated from 3D-magnetic resonance imaging and 3D-computed tomography differed (1238.1904 units and 1402.364 units respectively). The left lobe volume of the liver estimated with 3D-magnetic resonance imaging and 3D-computed tomography also differed (450.530 units and 554.490 units, respectively). The right lobe volume of the liver estimated with 3D-magnetic resonance imaging and 3D-computed tomography were 787.660 units and 847.545 units, respectively, while the actual average right lobe volume of the harvested liver was 678.636 units. 3D-computed tomography has been widely used to estimate the right lobe volume of the donors’ liver. However, 3D-magnetic resonance imaging was also very effective in estimating the volume of the liver. Thus, 3D-magnetic resonance imaging is also expected to become an important tool in determining the safety of the donors before transplantation.

In this paper, we suggest reliability as a metric to evaluate the robustness of a design for the optimal design of electromagnetic devices, with respect to constraints under the uncertainties in design variables. For fast numerical efficiency, we applied the sensitivity-assisted Monte Carlo simulation (S-MCS) method to perform reliability calculation. Furthermore, we incorporated the S-MCS with single-objective and multi-objective particle swarm optimization algorithms to achieve reliability-based optimal designs, undertaking probabilistic constraint and multi-objective optimization approaches, respectively. We validated the performance of the developed optimization algorithms through application to the optimal design of a superconducting magnetic energy storage system.

This paper presents an innovative design for a low-speed, direct-drive, axial-flux permanent-magnet (AFPM) generator with a coreless stator and rotor that is intended for application to small wind turbine power generation systems. The performance of the generator is evaluated and optimized by means of comprehensive 3D electromagnetic finite element analysis. The main focus of this study is to improve the power output and efficiency of wind power generation by investigating the electromagnetic and structural features of a coreless AFPM generator. The design is validated by comparing the performance achieved with a prototype. The results of our comparison demonstrate that the proposed generator has a number of advantages such as a simpler structure, higher efficiency over a wide range of operating speeds, higher energy yield, lighter weight and better power utilization than conventional machines. It would be possible to manufacture low-cost, axial-flux permanent-magnet generators by further developing the proposed design.

This paper discusses the development of a 3.5 kW switched reluctance motor (SRM)-based electric air-conditioning (AC) compressor, focusing primarily on the design aspects of the SRM and the integrated controller. In addition to the increased price of rare-earth magnets, SRM’s operation capability at high speed and high temperature makes the SRM a viable alternative to the permanent magnet motor for electrically driven automotive air conditioning compressors. A compact and energy efficient scroll compressor is designed and constructed. Two feasible SRM topologies are considered, in terms of efficiency, torque ripple, and acoustic noise. Compact drive electronics are designed and employed to drive the SRM-based compressor. The static and dynamic performance is validated by simulation and experiment.

In this paper, we examine the electrical and magnetic properties of three different types of shield materials used for wireless power transfer systems: namely, FeSiAl-composite, NiZn-ferrite, and FeSi-amorphous types. The power transfer efficiency and resistance of an RX coil are measured, while varying the shield thickness. For all three types, a thicker shield provides better power transfer efficiency. Analysis of the measurements shows that the FeSiAl-composite type is suitable for systems with size limitation. In terms of magnetic properties, the FeSiamorphous type shows the best features, and is suited to high power applications. This work can be used as a guideline to select suitable shielding material in various wireless power transfer systems.

Recently, module-integrated converter (MIC) research has shown interest in small-scale photovoltaic (PV) generation. The converter is capable of efficient power generation. In this system, the high frequency transformer should be made compact, and demonstrate high efficiency characteristics. This paper presents a core structure optimization procedure to improve the efficiency of a high frequency transformer of compact size. The converter circuit is considered in the finite element analysis (FEA) model, in order to obtain an accurate FEA result. The results are verified by the testing of prototypes.

This paper develops a moving-magnet electromagnetic actuator for fast steering mirror (FSM). The actuator achieves a reasonable compromise between voice coil actuator and piezoelectric actuator. The stroke of the actuator is between the strokes of a piezoelectric actuator and a voice coil actuator, and its force output is a linear function of air gap and excitation current within our FSM travel range. Additionally, the actuator is more reliable than voice coil actuator as the electrical connection in the actuator is static. Analytically modeling the actuator is difficult and time-consuming. Alternatively, numerous finite element simulations are carried out for the actuator analysis and design. According to the design results, a real prototype of the actuator is fabricated. An experimental test system is then built. Using the test system, the force output of the fabricated actuator is evaluated. The test results validate the actuator analysis and design.

This paper presents an eddy current loss analysis of a Mechanical Fixation (MF) made of 6061 aluminum alloy, which is used for an NS type double-rotor single-stator axial flux permanent magnet machine. The prototype MF made of aluminum alloy shows good mechanical performance, but poor electro-magnetic performance, since the machine’'s efficiency can decrease because of eddy current loss in the MF. In order to prevent efficiency decrease, a modification of the MF structure is also introduced. Three-dimensional finite element analysis (FEA) is used for magnetic field analysis, and eddy current losses are computed. The analysis results are compared to, and verified by the test results.