• 대한전기학회논문지:시스템및제어부문D
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• 제52권3호
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• pp.148-155
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• 2003

In this paper, a nonlinear anisotropic filtering method without the loss of important information happened due to the repeated filtering in magnetic resonance images is proposed. First of all original images are divided into four regions, e.g., SPR(Strong Plain Region), EPR(Easy Plain Region), SER(Strong Edge Region), and EER(Easy Edge Region). An optimal template among multiple templates is selected, then the nonlinear anisotropic filtering based on the template is applied in pixel by pixel basis. In the proposed algorithm, filtering strength of EER containing important information is adjusted very weak and filtering strength for remaining regions is also adjusted according to the degree of the importance. In spite of repeated filtering, resulting images by the proposed method could still preserve anatomy information of original images without any degradation. Compared to the existing nonlinear anisotropic filtering, the proposed filtering method with multiple templates provides higher reliability for filtered images.

• Journal of Magnetics
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• 제11권3호
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• pp.130-134
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• 2006

The microwave power absorption for the patterned CoNbZr magnetic film has been investigated by coplanar waveguide method. The power absorption peaks of the patterned CoNbZr film (50 ${\mu}m$ ${\times}$ 2 mm ${\times}$ 2 ${\mu}m$), were observed at around 5.7 GHz. The observed resonance peak was in good agreement with calculated ferromagnetic resonance frequency including magnetic shape anisotropy effects. Compared with the coplanar waveguide without a magnetic film, the characteristic impedance of patterned film was shown to be increased. This resulted from the large increment of inductance up to 33 % without any significant changes of the capacitance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.649-652
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• 1992

ECR(Electron Cyclotron Resonance) occure at ${\omega}_c$=${\omega}$, ${\omega}_c$:electron cycltron frequency, ${\omega}$:electromagnetic wave frequency. ECR system have several merit, 1) power transefer efficiency 2) low neutral gas pressure (below 1 mTorr) 3) high plasma density($10^{12}$ $cm^{-3}$). It is applicated variously in the field of semiconductor and new materials as the manufacturing equipment. Magnetic field in ECR system contruct resonance layer (${\omega}$=2.45GHz, $B_z$=875 Gauss) and control plasma. Plasma is almost generated at resonance layer. If the distance between substrate and resonance layer is short, uniformity of plasma is related with profile of resonance layer. Plasma have the property "Cold in Field", so directonality of magnetic field is one of the control factors of anisotropic etching. In this study, we calculate B field and flux line distribution, optimize geometry and submagnet current and improve of magnetic field directionality (99.9%) near substrate. For the purpose of calculation, vector potential A(r,z) and magnetic field B(r,z), green function and numerical integration is used. Object function for submagnet optimization is magnetic field directionality on the substrate and Powell method is used as optimization skim.

• Journal of Korean Neurosurgical Society
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• 제66권2호
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• pp.172-182
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• 2023

Objective : The blood-brain barrier (BBB) is an obstacle for molecules to pass through from blood to the brain. Focused ultrasound is a new method which temporarily opens the BBB, which makes pharmaceutical delivery or removal of neurodegenerative proteins possible. This study was demonstrated to review our BBB opening procedure with magnetic resonance guided images and find specific patterns in the BBB opening. Methods : In this study, we reviewed the procedures and results of two clinical studies on BBB opening using focused ultrasound regarding its safety and clinical efficacy. Magnetic resonance images were also reviewed to discover any specific findings. Results : Two clinical trials showed clinical benefits. All clinical trials demonstrated safe BBB opening, with no specific side effects. Magnetic resonance imaging showed temporary T1 contrast enhancement in the sonication area, verifying the BBB opening. Several low-signal intensity spots were observed in the T2 susceptibility-weighted angiography images, which were also reversible and temporary. Although these spots can be considered as microbleeding, evidence suggests these are not ordinary microbleeding but an indicator for adequate BBB opening. Conclusion : Magnetic resonance images proved safe and efficient BBB opening in humans, using focused ultrasound.

• Journal of Magnetics
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• 제11권2호
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• pp.90-94
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• 2006

A finite-element method is used to analyze loss generation and electromagnetic noise absorption characteristics of a coplanar waveguide transmission line integrated with a magnetic thin film. Parameters used in the analysis are the electrical resistivity of the magnetic layer and the thickness of both magnetic and insulating layers. The results indicate that L-C resonance is the main loss mechanism of the electromagnetic noise absorption.

• 한국초전도ㆍ저온공학회논문지
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• 제17권1호
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• pp.36-39
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• 2015

Many studies are being conducted to implement wireless charging, for example, for cellular phones or electronic tooth brushes, via wireless power transmission technique. However, the magnetic induction method had a very short transmission distance. To solve this problem, the team of Professor Marin Soljacic proposed a magnetic resonance system that used two resonance coils with the same resonance frequency. It had an approximately 40% efficiency at a 2m distance. The system improved the low efficiency and short distance problems of the existing systems. So it could also widen the application range of wireless power transmission. Many studies on the subject are underway. In this paper, the superconductor coil was used to improve the efficiency of magnetic resonance wireless power transmission. The resonance wireless power transmission system had a source coil, a load coil, and resonance coils (a transmitter and a receiver). The efficiency and distance depended on the characteristics of the transmitter and receiver coils that had the same resonance frequency. Therefore, two resonance coils were fabricated by superconductors. The current density of the superconductor was higher than that of the normal conductor coil. Accordingly, it had a high quality-factor and improved efficiency.

• Journal of Power Electronics
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• 제19권3호
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• pp.637-644
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• 2019

Wireless power transfer (WPT) technology with various transfer mechanisms such as inductive coupling, magnetic resonance and capacitive coupling is being widely researched. Until now, power transfer efficiency (PTE) and power transfer capability (PTC) have been the primary concerns for designing and developing WPT systems. Therefore, a lot of studies have been documented to improve PTE and PTC. However, power consumption in the standby mode, also defined as the no-load mode, has been rarely studied. Recently, since the number of WPT products has been gradually increasing, it is necessary to develop techniques for reducing the standby power consumption of WPT systems. This paper investigates the standby power consumption of commercial WPT products. Moreover, a standby power reduction technique for WPT systems via magnetic resonance coupling (MRC) with a parallel resonance type resonator is proposed. To achieve a further standby power reduction, the voltage control of an AC/DC travel adapter is also adopted. The operational principles and characteristics are described and verified with simulation and experimental results. The proposed method greatly reduces the standby power consumption of a WPT system via MRC from 2.03 W to 0.19 W.

• 한국초전도ㆍ저온공학회논문지
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• 제17권2호
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• pp.31-35
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• 2015

Mapping is a useful tool in the magnetic field analysis and design. In some specific research area, such as the nuclear magnetic resonance (NMR) or the magnetic resonance imaging (MRI), it is important to map the magnetic field in the interesting space with high accuracy. In this paper, an indirect mapping method in the center volume of an air-core solenoid is presented, based on the solution of the Laplace's equation for the field. Through the mathematical analysis on the mapping calculation, we know that the condition number of the matrix, generated by the measurement points, can greatly affect the error of mapping result. Two different arrangement methods of the measurement points in field mapping are described in this paper: helical cylindrical line (HCL) method and parallel cylindrical line (PCL) method. According to the condition number, the HCL method is recommended to measure the field components using one probe. As a simple example, we mapped the magnetic fields in a MRI main magnet system. Comparing the results in the different methods, it is feasible and convenient to apply the condition number to reduce the error in the field mapping calculation. Finally, some guidelines were presented for the magnetic field mapping in the center volume of the air-core solenoid.

• 한국자기공명학회논문지
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• 제17권2호
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• pp.92-97
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• 2013

We study the electron spin resonance line-width (ESRLW) of $Fe^{3+}$ in crystalline $LiNbO_3$ ; the ESRLW is obtained using the projection operator method (POM) developed by Argyres and Sigel. The ESRLW is calculated to be axially symmetric about the c-axis and is analyzed by the spin Hamiltonian with an isotopic g factor at a frequency of 9.5 GHz. The ESRLW increases exponentially as the temperature increases, and the ESRLW is almost constant in the high-temperature region (T>8000 K). This kind of temperature dependence of the ESRLW indicates a motional narrowing of the spectrum when $Fe^{3+}$ ions substitute the $Nb^{5+}$ ions in an off-center position. It is clear from this feature that there are two different regions in the graph of the temperature dependence of the ESRLW.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.314-324
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• 1996

A high speed NMR quality evaluation sensor was designed , constructed and tested . The device consists of an NMR spectrometer coupled to a conveyor system. The conveyor was run at speeds ranging from 0 to 250 mm/s. Spectral of avocado fruits and one-dimensional magnetic resonance images of pickled olives were acquired while the samples were moving on a conveyor belt mounted through a 20Tesla NMR magnet with a 20 mm diameter surface coil and a 150 mm diameter imaging coil respectively. Fro a magnetic resonance spectrum analysis, motion through variations in the magnetic field tends to narrow spectral line width just like using sample rotation in high resolution NMR to narrow spectral line width. Spectrum analysis was used to detect the dry weight of avocado fruits using the ratio oil and water resonance peaks. Good correlations maximum r=0.970@ 50 mm/s and minimum r=0.894@250mm/s ) between oil and water resonance peak ratio and dry weight of avocados were observed at speeds ra ging from0 to 250mm/s. For the application of magnetic resonance imaging (MRI) method, the projections were used to distinguish between pitted and non-pitted olives . Effect of fruit position in the coil was tested and coil degree effects were noticed when projects were generated under dynamic conditions. Various belt speeds (up to 250mm/s) were tested and detection results were compared to static measurements. Higher classification errors were occurred at dynamic conditions compared to errors while olives were at rest.