Verifying magnetic anisotropy is essential for developing flexible magnetic devices. The magneto-mechanical effect is a unique phenomenon in magnetic materials for bending geometries and produces the stress magnetic anisotropy depending on the stress direction and its magneto-striction coefficient. In addition, the fabrication process for the flexible magnetic devices, such as deposition, annealing, and patterning, significantly causes the intrinsic magnetic anisotropy to change the reversal behaviors in the devices. This study investigated the variation of the stress magnetic anisotropy in the flexible NiFe (permalloy) thin films as a function of the bending repetition and its direction when the thin films had a different easy axis caused by the sputtering process. The variation of the stress magnetic anisotropy was observed by the magnetization reversal behaviors and the typical ferromagnetic resonance field detection before and after the application of the tensile stress. The stress effect was exponentially accumulated with increasing bending repetition on the thin film in both samples. However, when the repeated stress was applied in alternating x- and y-directions, minor resonance field fluctuation was observed in the film, which had the tilted intrinsic magnetic anisotropy. This result indicated that intrinsic magnetic anisotropy during the fabrication process played an essential role in determining the amount of effective field for designing flexible magnetic devices.

Spin Hall magnetoresistance (SMR) emerges from both spin Hall effect (SHE) and inverse spin Hall effect (ISHE), which is usually investigated in a nonmagnetic heavy metal (NM) in contact with a ferromagnet (FM). Depending on the orientation of FM magnetization and spin polarization of NM layer, the transmission or reflection of the spin current at the FM\NM interface could occur. SMR was investigated in 1.5 nm NiFe\3.0 nm IrMn₃\3.0 nm Pt magnetic heterostructures. IrMn₃ thin film grown on ferromagnetic NiFe layer exhibits the glassy magnetic behavior and displays spin reorientation transition in the magnetic field-temperature space. Below the Néel temperature of IrMn₃, the angle dependence of MR measurement in the xy and xz plane showed a normal positive SMR. However, a sign change in SMR was observed in the magnetic field applied in the yz plane. The switching from negative to positive SMR occurs at the field above a critical value of 6 kG. Our results provide a potential advantage for the source of spin flow in the signal in multilayer heterostructures and highlight the importance of magnetic structure (Néel vector) in AF, which opens the possible way to manipulate the spin current transportation and AF memory devices.

We report our experimental investigation on the temperature-dependent hysteresis loops and magnetic domain behaviors of CoFeB (0.4 nm)/Pd (1 nm) multilayer on polyimide substrate with a perpendicular magnetic anisotropy, by means of magneto-optical Kerr microscopy. Hysteresis characteristics such as saturation magnetization, coercivity, and hysteresis loop area with respect to the temperature have been analyzed, where power-law scaling behaviors are observed with microscopic magnetic domain patterns mediated by numerous nucleation sites.

Owing to extensive application developments of nanofluid, the engineers and scientists have concentrated their attention in regions of thermal and engineering processes. Additionally, nanofluids have wide-ranging returns as compared to traditional fluids. Keeping aforementioned logicality of nanofluid in observation, we deliberated a time-varying mathematical model to formulate the non-uniform heat sink-source assume Sutterby liquid over Brownian movements and thermophoretic. Thermal- solutal stratification phenomenon in addition with heat sink-source and activation energy aspects are scrutinized. Characteristics of random motion and thermophoresis diffusion properties for Sutterby fluid are examined. Similarity variable techniques are used to reduce partial differential equations into ordinary differential equations and solved numerically by using bvp4c method. The physical aspects of fluid flow, temperature, concentration for variation of involved parameters have been explained through graphs. Velocity of Sutterby nanofluid has contrary performances against unsteady and mixed convection parameters. Augmented values of Brownian moment, thermophoresis and heat source parameters exaggerate the temperature of nanofluid. Concentration of Sutterby nanofluid deteriorates for greater Schmidt number. Moreover, transportation rate of heat dwindles against Pr while it rises against N_t.

Recently, the method of designing motors according to the high voltages of vehicle systems has been reestablished; in the case of traction motors for electric vehicles (EVs), which are large devices, hairpin winding structures have been increasingly adopted for improved outputs and efficiencies. However, for hairpin windings, significant AC losses can occur in EV systems requiring high driving speeds, thereby decreasing the efficiencies in high-speed operation regions. Therefore, this study designs a motor that uses a round wire winding and a hairpin winding under the same vehicle system conditions and analyzes the suitability of the hairpin structure for application to an EV traction motor under the current vehicle system condition.

The fluorine salt oxide molten-salt electrolytic Dy-Cu alloy was used as a grain boundary diffusion source instead of the doped Dy-Cu alloy. The microstructure and coercivity of the GBDPed magnets with the different diffusion times were studied. The results show that the coercivity increased with the increase in the GBDP time. The ability of the electrolytic Dy-Cu alloy to improve the coercivity of Nd-Fe-B is more advantageous than that of the doped Dy-Cu alloy. Microstructure analysis shows that the segregation and metal inclusion, a small amount of Dy₂O₃, and the poor synergy diffusion between Dy and Cu lead to the unsatisfactory performance of the doped Dy-Cu alloy to improve the coercivity. The diffusion rate and depth of the GBD source improved by replacing the doped alloy with an electrolytic alloy.

The casting process of Fe-Ni Invar alloy could drastically affect magnetic properties and thermal expansion. We have observed analogous trends of saturation magnetization and thermal expansion coefficient in two distinct types of casted samples, as we perform post-annealing at different temperatures. X-ray diffraction measurements show that all the alloys remain in the same face-centered cubic structure after different heat treatments without phase transformation. With the help of X-ray diffraction and differential thermal analysis, we have inferred that these changes in properties might be induced by magnetic lattice transitions and analyzed the possible reason for property differences in samples. This work delivers a perspective on the relationships between thermal expansion, magnetic properties, and heat treatments, which could help to improve the industrial assembly line design.

This paper proposes a method for the electromagnetic field analysis of permanent magnet synchronous motors (PMSMs) considering the axial leakage flux. To the axial leakage flux while employing two-dimensional (2D) finite-element analysis (FEA), the permeance of the axial leakage path is added into a slot region by increasing the permeability of elements in that region. The increased permeability is calculated based on the permeance relationship of the main magnetic and axial leakage paths, which are calculated using the equivalent magnetic circuit method. The effect of the proposed method is verified by comparing it with the 3-dimensional FEA results. The proposed coupling method uses finite element analysis and is developed from the lumped method proposed in our previous research. The developed method enables the analysis of distributed winding machines, which is not possible with the existing method.

The suppression of cytokine storm in severe coronavirus disease 2019 (COVID-19) patients can be treated with monoclonal antibody therapy against CD3 for T cell receptor inhibition. An optimized liquid phase as a CD3 antibody-magnetic nanoparticle (Ab-MNP) conjugate can inhibit the overactivation of T cells. We aim to analyze the distribution of Fe in the spleen after acute administration of silica-conjugated amine magnetite (Fe₃O₄) nanoparticles (35 nm) delivered by intravenous injection. The Fe element distribution and concentration levels in spleen tissue were analyzed using energy dispersive spectroscopy (EDS) and inductively coupled plasma-mass spectrometry (ICP-MS). The experimental result is a difference in the concentration of Fe elements, which was 1.89×10³ mg/kg in the spleen of a control mouse not administered with MNPs, whereas increases significantly to 1.93×10³ mg/kg in that of a mouse administered with MNPs. Further, time kinetic analysis of biochemical and immunological parameters is required to confirm its suitability in bio-administration.

With the enhancement of national income level, the number of computed tomography (CT) exams to diagnose diseases is increasing more and more. To utilize the data for the safety control of X-ray, the image quality of the environmental radiation at the boundaries in the radiation zone of the exam rooms by type of CT using high-energy electromagnetic wave. The locations of the environmental radiation measurement were shielding wall of the door for patients, door for patients, door to CT control room, shielding wall of the door for CT control room, and window to see the patients, and the glass dosimeters were installed 150 to 170 cm above the floor considering the location of the device to be measured for 3 months and analyzed. The environmental radiations in the MDCT room were measured with 3.09 ± 2.31 mSv, 0.51 ± 0.12 mSv, 0.99 ± 0.43 mSv, 0.27 ± 0.03 mSv, and 0.18 ± 0.03 mSv at the door to the control room, the wall of the control room, door for patients, door wall, and window to see the patients, respectively. In the mobile CT room, the radiation was detected only at the door of the control room with 1.65 ± 0.15 mSv, and no radiation was detected at the other boundaries. In the PET-CT room, the radiations were detected with 0.18 ± 0.03 mSv and 0.27 ± 0.03 mSv at the door and door wall, respectively, without detection at the other boundaries. Upon the results of image quality by CT devices, very satisfactory outcomes were found in terms of contrast, clarity of the boundaries, and detection rate of lesions in all the acquired images, and also very satisfactory in the functional evaluations of the organs in PET-CT only. These results are anticipated to be used as the reference data to establish the systemic and efficient systems and policies in the safety control of X-ray in the future.

*These authors contributed equally to this work.

These authors contributed equally to this work.

These authors contributed equally to this work.

Treatments demanding high accuracy, such as intensity-modulated radiation therapy (IMRT), should provide the optimal dose distribution and correct intervention. Otherwise, they may become unsafe and cause adverse effects to patients. Delivery quality assurance (DQA) for treatment verification can be performed considering the absolute dose using an ionization chamber and relative dose using a film. However, a film imposes a long waiting time for measurement and is sensitive to temperature and humidity, development conditions, and noise. We aim to evaluate the usefulness of a multipurpose phantom for fast and simple IMRT DQA. The multipurpose phantom is made of poly (methyl methacrylate)-based resin. The phantom allows the insertion of a 2D array detector and an ionization chamber. Therefore, the relative and absolute doses can be measured simultaneously. The IMRT DQA evaluation provided absolute dose of 0.35 ± 1.74% and relative dose of 99.03 ± 0.6 % in 3 mm/3% gamma evaluation for a linear accelerator. In addition, the absolute and relative doses were 1.37 ± 1.05% and 98.7 ± 0.78% in helical tomotherapy, respectively. Therefore, the dose measurements were within acceptable error limits of 3%. The results demonstrate the multipurpose capabilities of the proposed phantom for evaluating dose distribution and absolute dosimetry.

This study verifies the feasibility and optimal conditions for using a general-purpose x-ray imaging device with a relatively large detector and excellent image quality compared to dental x-ray imaging devices according to international standards. The dental material test specimens were produced in the form of disks from four companies with different radiopacity, and aluminum step wedges was manufactured according to ISO 13116. In order to find the optimal irradiation conditions for general X-ray imaging devices, the distance between the target and the tube was fixed at 700 mm, and the exposure time was fixed at 100 ms. And the tube voltage was 50, 60, 70 kV and the tube current was changed to 40, 80, and 160 mA. As a result, it was sufficient to use general-purpose X-ray imaging devices, and the best results were obtained under the optimal conditions of 60 kV and 40 mA.

In order to increase the qualitative value of MRI and reduce the relative image acquisition time, the mutual intersection of Partial Fourier and Average was conducted to evaluate image distortion and acquisition time according to the effects of FID and Susceptibility Artifact in the T1 3D SPACE Sequence. As a result of analyzing the Roundness (%) of the phantom for Gd contrast agent concentration, when the Partial Fourier 8/8 was fixed, as the Average increased, the Roundness (%) increased (distortion decreased). When the Average 2.0 was fixed, as the Partial Fourier was reduced, the Roundness (%) decreased (distortion increased). As a result of Correlation analysis on Roundness (%), Partial Fourier and Average showed a high positive correlation. Experimental results on image distortion and acquisition time when using the T1 3D SPACE sequence showed that reducing the Partial Fourier than the Average reduced the image distortion and shortened the acquisition time.

The purpose of this study was to compare the use of different frequencies of repetitive transcranial magnetic stimulation (rTMS) on the upper extremity muscle activity and hand function of chronic stroke patients. The study subjects comprised 18 chronic stroke patients: the 5 Hz rTMS group (HFG), which included nine patients who received rTMS to the affected cerebral hemisphere, and the 1 Hz low-frequency group (LFG), which had nine patients who received rTMS to the nonaffected cerebral hemisphere. The intervention was conducted three times a week for four weeks. Electromyography was used to check muscle activity, and the stroke upper extremity function test (MFT) and grip strength test were performed to check hand function. Pre- and post-evaluations were performed for both groups. A comparison between the two groups showed a significant difference in the activity of the trapezius anterior and triceps brachii muscle for the muscle activities in the HFG group (p < 0.05) as well as a significant difference in the MFT results for hand function (p < 0.05). In the LFG group, a significant difference was noted in the triceps brachii muscle for muscle activity (p < 0.05), but no significant difference was evident in hand function (p > 0.05). The comparison of the two groups showed a significant difference in muscle activity in the triceps brachii muscle (p < 0.05) but no significant difference in hand function (p > 0.05). This study confirmed that high-frequency rTMS has a positive effect on upper extremity muscle activity and hand function in chronic stroke patients.

An intervention program was conducted with two groups of patients who had experienced stroke: one which received low-frequency rTMS and occupational therapy (rTMS-OT Group), and one which received occupational therapy only (OT group). The treatment was provided three times per week for 4 weeks followed by a 1-week evaluation of MEP amplitude and latency, and muscle tone. In an intergroup test of MEP amplitude and latency, and muscle tone, all groups showed increases between pre-and post-test evaluations. As a result of the study, during the treatment intervention of the experimental group and the control group, the experimental group rTMS-OTG and the control OTG group showed MEP amplitudes of 0.161 mV and 0.114 mV, respectively, and the experimental group showed more improvement. The MEP latency of the rTMS-OTG group was -2.83 ms and the MEP latency of the OTG group was -1.49 ms. The experimental group, rTMS-OTG, responded faster. However, in the case of muscle tone evaluation, there was no significant difference between the two groups. In conclusion, we determined that rTMS may be safely applied to the directly damaged cerebral cortex and is considered to be an effective treatment for patients recovering from stroke.

The thermoluminescent dosimeter is the most commonly used instrument for measuring radiation dose. Based on the previous study that the glow curve changes in the magnetic field environment of a thermal luminescence dose device, the change of the glow curve according to the change of the magnetic field strength is evaluated. Accordingly, the change in the glow curve was analyzed by irradiating 0.5-2 cGy to the thermoluminescent chips with a radiation generator while changing the magnetic field strength using a permanent magnet. As a result of the evaluation, an average increase of 0.3% was observed at 90~120 ℃, an average decrease of -10.6% at 120-160 ℃, and an average increase of 3.2% at 160-260 ℃. Therefore, when applying the thermoluminescent dosimeter, it is necessary to evaluate the dose considering the error rate according to the magnetic field strength.

To improve the spatial resolution of preclinical positron emission tomography (PET), a detector consisting of a two-layer scintillator pixel array was designed. A light guide was inserted between the arrays of scintillators to change the distribution of light generated in each layer. By analyzing the different light distributions, it is possible to track where the gamma rays interacted. To this end, a gamma ray event was generated at the center of the flashing pixel and a lookup table was created based on the signal obtained from the light sensor. The optimal position of the scintillation pixel was tracked through comparison and analysis of the newly detected signal with the look-up table through maximum likelihood position estimation. As a result, excellent accuracy was shown. If this detector is used in a preclinical PET system, it is expected to show excellent spatial resolution, and since an optical sensor that is not affected by magnetic fields is used, it is considered that it can be applied to PET/MRI in the future.

During radiation therapy, the mobility of the multi-leaf collimator varies according to the shape of the tumor and the angle of the collimator. Therefore, the purpose of this study is to understand the change in surface dose according to the collimator angle and the shape of the tumor. Using 10MV electromagnetic radiation, a treatment plan was implemented according to the length and short axis ratio of the tumor and the collimator angle, and the surface dose was compared with the actual measured value. As a result of the evaluation, the surface dose increased as the length of the tumor decreased and the angle of the collimator increased. If it is necessary to reduce the surface dose through this, the collimator angle should be applied in consideration of the short/long ratio.

These authors contributed equally to this work.

Mammography is one of the most important test techniques for screening and diagnostic examinations of breast diseases. Recently, the incidence of breast cancer has increased and the demand for mammography is increasing through the cancer screening programs in each country. Therefore, research on shielding materials is actively being pursued to reduce radiation exposure during mammography. The purpose of this study is to verify and compare the GATE simulation and experiment in terms of the shielding performance under the experimental conditions of tube voltage (25, 30, 35 kVp) and silicon thickness (1, 2, 3, 4, 5, 6 mm). Through MCNP simulation, the absorbed dose reduction rate of breast tissue according to tube voltage/silicon shielding thickness is presented. The GATE simulation and experimental results were within the error range of 0.07 to 1.42 % under all conditions. In addition, through simulations and experiments, it was confirmed that silicon can offer more than 80 % shield regardless of automatic exposure control (AEC) of mammography equipment when 5 mm of silicon is used. Therefore, the results of the study can serve as useful basic data for the development of a shielding suit or shield that can reduce the exposure of other surrounding tissues due to scattered rays during mammography.

This study aimed to develop a multichannel field programmable gate array (FPGA) based data acquisition (DAQ) system that could process 8 analog signals from a 1 × 8 LYSO array coupled with a Geiger-mode avalanche photodiode (GAPD) for fan-beam dual-energy X-ray absorptiometry (DEXA) system. Each analog input signal was digitized using an 8-channel analog-to-digital converter (ADC) with a 125 MHz sampling rate and an input range of -1.0 to 1.0 V. The 14-bit digital signals were then fed into a Xilinx Virtex-6 FPGA-based evaluation board that implemented digital signal processing logic. The collected low- and high-energy events of each pixel for each input channel were stored in an on-chip block ram-based first-in-first-out (FIFO) module, and then further transmitted to a personal computer (PC) via the USB port. The intrinsic characteristics, spectral responses, and image acquisition were performed. The estimated coefficient of determination (R²) was 0.999 in voltage linearity and no considerable alterations in voltage resolution were observed. The energy resolutions of the peak 59.5 keV (Am-241) were ~28.2 %. Dual-energy peaks were isolated in the X-ray energy spectra. The synchronization between the movement part of the DEXA system and the timing control block inside the FPGA chip was well controlled in various conditions. The DEXA phantom images for each pixel were clearly resolved. This study demonstrated that FPGA with only on-chip memory resources can be used to build a multichannel DAQ system for fan-beam DEXA systems.

The purpose of this study was to investigate the effect of 5Hz repetitive transcranial magnetic stimulation (rTMS) on cortical activity and upper limb function in the etiology of chronic stroke patients. 2 patients with ischemic stroke and 2 patients with hemorrhagic stroke who satisfied the selection criteria were selected using the ABA’ single subjective design. The study period was applied 18 times in all 4 patients: 3 times at baseline (A), 12 times in intervention period (B), and 3 times in baseline (A'). During intervention period(B), 5Hz rTMS was applied 4 times a week for 3 weeks, and no intervention was performed during the 3 baseline (A) and baselines (A’). Electroencephalography (EEG), box and block test (BBT), and fugl-meyer assessment (FMA) were performed to investigate changes in cortical activity and upper limb function. As a result, EEG and BBT were changed after intervention (B) in ischemic stroke patients than in hemorrhagic stroke patients, and there was no difference in FMA of all stroke patients. Through this, it is thought that 5 Hz r TMS can help to improve cortical activity and upper limb function in ischemic stroke rather than hemorrhagic stroke.

The aim of the study was to compare the image quality of reconstructed images using the 3D T1 variable flip angle (CUBE) sequence with and without compressed sensing (CS). A phantom was prepared by diluting the Gadolinium contrast medium with saline at the concentrations of 0, 0.2, 0.6, 1.0, and 4.0 mM. Moreover, images were obtained using the 3D T1 CUBE sequence with and without the use of CS. When CS was used, images were reconstructed at increasing CS factor values (i.e., 1.2, 1.4, 1.6, 1.8, and 2.0), while all other variables were unaltered. Measurements were analyzed using Student’s t-tests and ANOVA. Moreover, the SSIM and RMSE estimates were evaluated using the ICY program and the relative SNR errors were quantified. The scan time reduced by up to 1min 35sec from the conventional 3D T1 CUBE sequence (3min 3sec) to 3D T1 CUBE sequence using CS (CS factor=2.0). The SNR values of the conventional 3D T1 CUBE and 3D T1 CUBE sequences using the CS technique were not significantly (p>0.05) different when the CS factors varied from 1.2 to 2.0. Moreover, the estimated SSIM were similar, while the root mean square error (RMSE) values varied when the CS factor varied from 1.2 to 2.0, based on the use of the conventional 3D T1 CUBE sequence. Therefore, the 3D T1 CUBE sequence using the CS technique can achieve an acceptable image quality that is not considerably different from that of the conventional method.