The effects of oxygen vacancies and strain on the magnetism and Curie temperature of La_0.7Sr_0.3MnO₃ (LSMO) thin films deposited by PLD are investigated by changing oxygen partial pressure and increasing the interface mismatch between LSMO and SrTiO₃. The presence of oxygen vacancies reduces the double exchange effect between Mn³⁺ and Mn⁴⁺ ions, and the high-quality crystals effectively increase the Curie temperature of LSMO. Moreover, SrTiO₃ simultaneously exerts strain on the upper and lower interfaces of the LSMO film to promote orbital reconstruction of the e_g electrons in the Mn³⁺ ions. These electrons preferentially occupy the e_g(x²-y²) orbit and lead to an enhancement in the in-plane ferromagnetic exchange effect, thereby increasing the Curie temperature. These results suggest that the magnetic properties of these materials can be controlled through artificial structure design and provide guidance for their application in high Curie temperature spintronic devices.

In this work, the soft-template technique was employed in preparing the superparamagnetic Fe₃O₄ nanoparticles from natural iron sand. A series of the Fe₃O₄ nanoparticles formed spinel crystal structure with the particle size in the range of 1.9 to 6.6 nm which was varied by diethylamine concentration as the template. All samples had the functional groups of Fe³⁺-O²⁻, Fe²⁺-O²⁻ and OH and exhibited the superparamagnetic character. The antibacterial activity of the Fe₃O₄ nanoparticles showed a significant outcome to pathogen growth rate. Pre-administration of bacterial stock solution (E. coli and B. substilis) with magnetite significantly reduced the colony formation compared to control group. In particular, for Gram-negative bacteria growth rate, pretreatment with magnetite declined the colony formation considerably compared to placebo and positive control group. Also, in line with Gram-negative bacteria, the similar pattern of the bacterial killing property was observed in Gram-positive bacteria.

We investigated the magnetotransport properties in SrRu_0.7Fe_0.3O_3-δ epitaxial thin film synthesized by using pulsed laser deposition. X-ray diffraction (XRD) θ − 2θ and reciprocal space mapping scans showed strong peaks demonstrating high quality. The image of step and terrace at atomic force microscope scan image of the film showed a layer by layer growth mode of the thin film. The resistivity showed a significant decrease by applying magnetic field of 9 T, which could be described in terms of spin dependent scattering. The zero-field resistivity at low temperature (2 K-24 K) was fitted very well with a variable range hopping model. The observed negative magnetoresistance (T = 10 K, H = 9 T) was as high as ~20%.

The major factors that limit the application prospects of Switched Reluctance Motor (SRM) include torque ripple, noise and vibration. The main reason attributed to these drawbacks is the nature of flux linkage variation in accordance with rotor position. In this aspect this work analyses the effect of embedding permanent magnets in the stator and the impact of their orientation on the flux linkage characteristics and hence on the performance of the motor. In addition the effect of lamination material on the characteristics of the motor is analysed. The materials considered include M850-65A, M-19, M-43, Pure Soft Iron, and M800-50D. This paper proposes, the optimization of Permanent Magnet Flux Reversal Free Switched Reluctance Motor (PMFRFSRM) through the orientation of permanent magnets and choice of suitable laminating materials to improve the performance characteristics of the motor. The analysis is performed using Finite Element Analysis (FEA) based package MagNet and the results are validated with hardware prototype.

The traditional magneto-optical Kerr effect (MOKE) measurements involve measuring the intensity of a light reflected off the samples subjected to a DC magnetic field. By superimposing an AC field to the sweeping DC field, and measuring the AC component of the light intensity, we achieved a high signal-to-noise ratio and a better resolution in determining the Curie temperatures of magnetic samples. For a demonstration, we have determined the Curie temperature of a 350 nm thick YIG (yttrium iron garnet, Y₃Fe₅O₁₂) thin film to be 511.0 +/−0.5 K using this method.

The purpose of this study was to provide preliminary experimental data on the utility of a new oral contrast media for abdominal MRI contrast imaging examination. In the experimental study, the following oral contrast media were used: Solotop^® (Taejoon Pharmacal, Seoul, Korea), diatrizoate meglumine (Gastrografin^®, Schering, Berlin, Germany), 50 % blueberry juice, 100 % orange juice, 3.5 % blueberry juice. The GE Signa Excite HD 1.5 T MR system and an 8-channel CTL (cervical thoracic lumbar) coil were used to obtain. T1- and T2-weighted images, and the acquired SNR and CNR values of the contrast media were analyzed by multi-way ANOVA. Fruit juice was lower than water in T2-weighted images and showed relatively higher contrast than did chemical contrast media. On the other hand, T1-weighted images showed a relatively low-contrast effect due to the moisture contained in the fruit juice. For the T1-weighted images, Gastrografin^® and Solotop^® had higher CNR and SNR than did the fruit juice contrast media. There was a statistically significant difference between water and oral contrast media (p < .05). Fruit juice having lower absolute water content than water showed lower T2 signal value than did water. Fruit juice having a viscosity higher than that of water had the advantage of being able to get distributed evenly in a desired organ. With further advanced studies based on these experimental results, an alternative oral contrast media could be developed, and abdominal MRI could be expected to be actively applied in clinical practice.

Clinically acceptable scan time is very important in DTI which is essential for neurologic imaging and there have been ongoing efforts to make the scan time faster. Multi-Band SENSE simultaneous multi slice, also called multiband, is a better solution to reduce scan time. In order to compare the performance of SENSE and MB-SENSE on DTI acquisitions images were acquired using ACR phantom with factor 2 on both groups. The MB-SENSE group showed lower SNR values of center and peripheries than the SENSE in slice 7 (8.78 % and 8.99 % respectively). However, SNR loss is minimal. The SNR values profiles showed a equality from the center to peripheries of the image slice at both MB-SENSE and SENSE. The difference of SNR profiles was approximately 3 % at the center and 9 %-15 % at peripheries at SENSE. This became 3 % at the center and 10 %-15% at peripheries at MB-SENSE. Therefore, this study has studied and verified the effect of MB-SENSE in temporal resolution over SENSE which are applied on DTI technique using ACR QA program.

The present study aims to confirm the attenuation correction (AC) in positron emission tomography (PET) images using various magnetic resonance (MR) sequences with and without the MR breast radiofrequency (RF) coil, and thus to evaluate the attenuation effect of the MR breast RF coil. To that purpose, we reconstructed non-attenuated PET data using the MR AC_Dixon-CAIPI, MR AC_UTE, and MR AC_Dixon-GRAPPA sequences. The results indicated that the signal loss of the PET image with the MR breast RF coil was the lowest when the MR AC_Dixon-GRAPPA sequence was applied. In conclusion, the MR AC_Dixon-GRAPPA sequence maintained PET image quality when using the MR breast RF coil during PET/MR scanning.

In this paper, magnetic field heat treatment was carried out for the SmCo₅/α-Fe amorphous powders prepared by high-energy ball milling. The effects of annealing temperature and magnetic field on the crystallization, microstructure, and magnetic properties of the SmCo₅/α-Fe nanocomposite permanent magnets were studied. The results show that the magnetic field can benefit the crystallization of SmCo5 phase and the degree of crystallinity of SmCo₅/α-Fe alloy. Thus, the remanence and coercivity of the SmCo₅/α-Fe magnets annealed with magnetic field are significant higher than those of the samples annealed without magnetic field. With the increase of annealing temperature in magnetic field heat treatment, the Sm(Co, Fe)₅ phase and FeCo phase are gradually crystallized and grew up, while a small amount of Sm₂Co₁₇ phase appears. The best magnetic properties are M_r = 73.29 emu/g, M_r/M_s = 0.59, and H_ci = 6.20 kOe, when the annealing temperature is 700 ℃.

Permanent magnet machines are suitable for Hybrid Electric Vehicle (HEV) and Electric Vehicle (EV) application because of its superior torque density, high efficiency and small size. Especially, Interior Permanent Magnet Synchronous Motor (IPMSM) is an appropriate type because an air-gap flux density can be maximized and reluctance torque is enhanced using the saliency of rotor shape. However, a leakage flux generated in a magnetic rib which circulates inside the rotor and causes the decrease of the air-gap flux density. In this paper, an improved rotor structure is proposed where the magnetic ribs are removed and centre bridges are added for the mechanical stiffness. The air-gap flux density increased because two leakage paths are reduced to one path which are the magnetic ribs and the centre bridge respectively. In addition, the mechanical strength are analysed and compared. Finally, the improved model is manufactured and test is conducted for the verification.

To harvest the kinetic energy from the vehicle suspension system, a tubular generator, which is composed of a single permanent magnet layer coreless model, was proposed in the previous study. Despite the excessive volume of the generator, both output power and power density are significantly lower than other conventional machines. This paper examines different designs of the tubular generator with the goal to enhance the performance, including a double permanent magnet layers coreless model and a cored model. By using a commercial finite element method (FEM) software, two proposed generators are theoretically analyzed and compared with the conventional generator. Analyzed results reveal that under the same operating conditions, the cored model can regenerate the largest amount of the power density. These results indicate that cored model can be considered as a promising candidate for the application to the electromagnetic shock absorber in sport utility vehicle (SUV).

The anisotropic hot deformed nanocyrstalline Nd–Fe–B magnet was prepared by spark plasma sintering technique using MQU-F powders. The location dependence along radial direction on the magnetic properties, microstructure and crystal alignment of the hot deformed magnet have been investigated. The inhomogeneity of the magnetic performance along radial direction was revealed with a vibrating sample magnetometer (VSM). The crystal structure and microstructure were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM), respectively. In addition, quantitative texture analysis was carried out based on the electron backscattered diffraction technique (EBSD). The experimental results reveal that the coordination of grain size and orientation of Nd–Fe–B grains leads to the inhomogeneities of magnetic performance.

The ferrofluid-based damper has been a subject of active research recently in depressing low-frequency vibration of rod due to its relative small viscous damping for the vibration pick-up system. In this work, a novel ferrofluid-based planar damper with magnetic spring is firstly proposed. Compared with the traditional ferrofluid-based damper with the elastic restoring force of ferrofluids, the novel damper is designed with steady magnetic spring to obtain a large relative displacement and dissipate external vibration energy efficiently. Experimental results show that the novel damper has a high damping performance. Under the same initial vibration amplitude of beam, the logarithmic decrement of the system with the novel damper is 31.5 times and 5.5 times larger than those of the system without damper and with the traditional damper, respectively. In addition, compared with the system with the traditional damper, the system with the novel damper can reduce damping time by half.

The use of V₂O₅ as a liquid phase sintering aid for BaFe₁₂O₁₉ is studied. Three weight % of V₂O₅ is added to a BaFe₁₂O₁₉ powder, samples are sintered at temperatures between 900-1250 ℃ and the effects of sintering aid addition on densification, microstructure, phase purity and magnetic properties are examined. Compared to BaFe₁₂O₁₉ without sintering aid addition, addition of 3 wt% V₂O₅ leads to a moderate improvement in densification behavior. Samples with 3 wt% V₂O₅ addition contain considerable amounts of Fe₂O₃ and Ba₃(VO₄)₂ second phases. The BaFe₁₂O₁₉ sample without sintering aid addition has a Magnetization-Field hysteresis loop typical of a hard ferrimagnetic material, whereas the 97 wt% BaFe₁₂O₁₉ - 3 wt% V₂O₅ sample has a hysteresis loop with reduced saturation magnetization and coercivity.

In order to investigate the residual magnetic field (RMF) variations of initially undemagnetized ferromagnetic materials, tensile tests were conducted on the U75V steel specimens under tensile load with increasing amplitudes. It is found that the fluctuation of the unidimensional RMF reduces with the increase of load in the elastic stage, and remains relatively stable during the plastic stage. An effective way for characterizing deformation stages of the undemagnetized specimen is proposed by analyzing the RMF signals outside the longitudinal axis of the specimen. The two-dimensional vector distribution of the RMF indicates that the specimen tends to be magnetized as a rectangular magnet with an N pole and S pole at two ends with the increase of load. The possible reasons underlying the experimental results are discussed on the basis of the theory of the interaction between dislocation and domain.

In order to solve the slipping problem of a two-arm-wheel combined inspection robot, a maglev system based on the magnetic field of a high voltage direct current (HVDC) is proposed. The magnetic system comprises of two parts: a magnetic levitation system and a magnetic drive system. The levitation component overcomes the gravity of the robot by the Ampere force generated by current-carrying coils in the magnetic field of HVDC. The drive component utilizes the Ampere force generated by current-carrying coils in the magnetic field of HVDC as the driving force. Simulation results of the model are compared with the calculated values. The results show that the magnetic levitation method and the magnetic drive method are theoretically feasible, and the model is accurate and effective, which is of great practical significance to the physical realization of the inspection robot.

The widest application of magnetic fluid is in magnetic fluid seals. The starting torque varying with temperature of magnetic fluid seal has limited its application in special seal field such as military industry. This paper firstly measure the starting torque of magnetic fluid seals under different temperature conditions from −55 ℃ to 70 ℃ after holding for 2.5 hours in a closed environment with uniform temperature. And the law of starting torque with temperature change is studied experimentally. The results show that the starting torque of the magnetic fluid seal changes unobvious at 25 ℃ or higher temperature. The starting toque of magnetic fluid seal increases with the decrease of temperature, and the causes of which are analyzed. The results of this study provide experimental and theoretical reference for reducing the staring torque of magnetic fluid seal in low temperature environment.

The harmonics of the induced voltage under load conditions cause the deterioration of the motor performance. It occurs when the peak value of the demand voltage exceeds the DC link voltage. In this paper, thus, to reduce the induced voltage harmonics under load conditions, an asymmetric rotor design method using the advanced inverse cosine function (AICF) is proposed. Using this method, the rotor shape is determined by considering the armature reaction under certain load condition. As a result, an improved concentrated flux synchronous motor (CFSM) achieving the required performance is designed. Lastly, the induced voltages waveforms of the proposed motors under the load conditions are compared through finite-element analysis (FEA) as well as experiments.

On the basis of particle structure analysis, this paper studies the conductive mechanism of magnetorheological elastomers (MRE), and verifies the MRE conduction mechanism model based on the combination of tunnel current and conduction current. The piezoelectric characteristic of MRE is analyzed theoretically and the basic theoretical model of piezoelectric is established. A set of MRE piezoelectric characteristic test device has been designed independently. The test device is used to test the resistance values of MRE samples prepared in this experiment. Finally, the test results of each group are analyzed and compared, and the results show that this element can realize the stability test of MRE piezoelectric conductivity. Under different orders of magnitude, the low particle volume content is more sensitive to the conductivity of MRE samples, and the current flowing through the MRE sample shows a significantly non-linear relationship with the voltage applied to the sample.

The tube voltage in computed tomography (CT) changes the Hounsfield Unit (HU) and affects the electromagnetic radiation therapy planning (RTP) dose calculation. In this study, physical factors (tube voltage, tube current) of CT were analyzed for their RTP effects. A CT density phantom (CTDP) was exposed to measure the HU with an RTP system while we controlled the physical factors. The human body phantom was exposed with different CT tube voltages (70 kVp, 80 kVp, 100 kVp, 120 kVp, and 140 kVp) and electromagnetic radiation dose calculations were performed with the RTP system. The HU decreased when tube voltage was increased, in particular, the largest gap was found in bone, which has a high density (1792 ± 54 at 70 kVp, 1065 ± 13 at 140 kVp). However, a remarkable HU gap was not observed with the changes in tube current. In RTP the calculated dose increased when the tube voltage was raised, in particular, we observed a 3 % gap in brain tissue and bone, a remarkable HU gap. The chest had a small HU gap because of its relatively low density. The RTP dose calculation with changes in tube voltage had a 3 % error, which is acceptable. However, it can be eliminated of because daily QA/QC was performed and a CT density curve with rational exposure condition can be applied to brain or spine patients who experience large errors. This method enables reduction of the error caused by the physical factors in CT.

Instead of relying on traditional medical electrotherapy, we seek to determine a more positive approach to early ischemic brain injury by researching the effect of applying a magnetic stimulation device in an SD mouse’s brain to stop apoptosis, where a 64-Bit-EISC Processor Core delivers transcranial magnetic stimulation (TMS). We determined the change of the post-ischemic stimulatory effects on the Bax, caspase-3, and immune-reactive perikarya over time by stimulating the mouse’s brain. c-Fos and Cox-2 were used to find a crucial determining factor regarding inflammation-related cytotoxicity. The cerebral ischemia caused a biochemical change in the brain tissue and increased the neuronal genes within a few minutes. The genes showed that these very fast reactions involve an early gene. Next, we found an approach that is more favorable than electrotherapy for the apoptosis that is caused by early ischemic brain injury by researching the c-Fos protein that changes large-brain neurons; this was achieved after we stimulated the ischemic mouse brain using a two-tank LLC resonant converter as part of the TMS experimental equipment.

In this paper, the human exposure to the magnetic field from a household induction cooktop is assessed using two different methods. For the first method, the magnetic field from an induction cooktop is measured and compared with the reference levels (RLs) in the EMF (electromagnetic fields) guidelines. For the second method, coupling factors are calculated by simulations of 3-D human models and equivalent sources according to the IEC 62311 standard. The equivalent sources are obtained based on the non-uniform spatial distribution of the measured magnetic fields. Using the coupling factor, the induced current density and electric field inside the human body are estimated, and compared with basic restrictions (BRs) in the EMF guidelines. The exposure indices are calculated for both methods and the results are compared. Also, the possibility of overestimation is investigated when the measured magnetic field is compared with the reference levels.

Energy harvesting has become a highly important technology due to the development of portable electronic devices. In this study, we developed a rotary-type portable electromagnetic energy-harvesting device for charging portable electronic devices from wind and water stream. The advantage of the developed device is that it does not use a mechanical shaft because it uses the magnetic axial coupling (magnetic force) between the turbine and the device. In other words, the turbine can be easily replaced depending on the energy source. Furthermore, the device can produce the electrical power of mW class at a low rotating speed. The device consists of four inducing magnets, 16 pick-up coils, and a coupling magnet for combination between the device and the turbine. The device generated 35.15 V_rms at 300 rpm (5 Hz), and the maximum conversion efficiency reached up to 13.52 % at 240 rpm. We are aiming for energy conversion at a low rotational speed under 400 rpm and the device achieved mW class conversion: 360 rpm produced approximately 14 mW. To verify the proposed methods, we conduced various experimental analyses.