• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.10
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• pp.1727-1730
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• 2016

Magnetic resonance imaging has a potential to produce clear anatomical as well as functional images of human body. However, the ability to diagnose is limited by signal to noise ratio (SNR) and the resolution of current medical systems. To remove the challenges prevalent due to the use of high field scanners, dedicated radio frequency coils are used. Transverse electromagnetic coils have an advantage of providing homogeneous magnetic field throughout the region but with low signal to noise ratio while surface coils have an advantage of providing higher signal to noise ratio but with low homogeneity. This research combines both the advantage into one by utilizing transmit only transverse electromagnetic radio frequency coils (8 channel) along with receive only surface coils (by varying the number) for better imaging of brain. A 7 Tesla 32-channel close fitting helmet shaped phased-array surface coils along with the combination of 8 channel transmit only transverse electromagnetic coils provided good homogeneity as well as significant SNR improvements throughout the human brain.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.8
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• pp.1010-1013
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• 2012

This paper demonstrates the use of the convex optimization to localize the transverse magnetic $B_1^+$ field in regions of interest for recently proposed multi-sectioned alternating impedance coils and the traditional transmission line coil. An approach based on different axial slices to identical RF coils except upper stripline structure is investigated. Electromagnetic simulation results are compared for RF coils and discussed in detail at 7.0 T.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.3
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• pp.429-432
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• 2015

Radio Frequency (RF) coils in Magnetic Resonance Imaging (MRI) systems interact with a patient's tissues, resulting in the absorption of RF energy by the tissues. The presence of an electrically conducting medical implant may concentrate the RF energy and causes tissue heating near the implant devices. Here we present a novel design for a medical lead to reduce this undesired heating. Specific Absorption Rate (SAR), an indicator of heating, was calculated. Remcom XFdtd software was used to calculate the peak SAR distribution (1g and 10 g) in a realistic model of the human body. The model contained a medical lead that was exposed to RF magnetic fields at 64 MHz (1.5 T MRI), 128 MHz (3 T MRI) and 300 MHz (7 T MRI) using a model of an MR birdcage body coil. Our results demonstrate that, our proposed design of adding nails to the medical lead can significantly reduce the SAR for different MRI systems.

• Investigative Magnetic Resonance Imaging
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• v.24 no.2
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• pp.67-75
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• 2020

When a patient takes an MRI scan, the patient has a risk of unexpected injuries due to the intensive electromagnetic (EM) field. Among the injuries, the tissue heating by the time-varying EM field is one of the main issues. Since an implanted artificial structure with a conductive material aggravates the heating effect, lots of studies have been conducted to investigate the effect around the implants. In this review article, a mechanism of RF heating around the implants and related studies are comprehensively investigated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2019-2022
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• 2016

In the presence of an electrically conducting medical lead, radio frequency (RF) coils in magnetic resonance imaging (MRI) systems may concentrate the RF energy and cause tissue heating near the lead. A novel design for a medical lead to reduce this heating by introducing pins in the lead is presented. Peak 10 g specific absorption rate (SAR) in heart tissue, an indicator of heating, was calculated and compared for both conventional (Medtronic) lead design and our proposed design. Remcom XFdtd software was used to calculate the peak SAR distribution in a realistic model of the human body. The model contained a medical lead that was exposed to RF magnetic fields at 64 MHz (1.5 T), 128 MHz (3 T) and 300 MHz (7 T) using a model of an MR birdcage body coil. The proposed design of adding pins to the medical lead can significantly reduce the heating from different MRI systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.6 s.121
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• pp.648-655
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• 2007

In this paper, we introduce a dual coil antenna which is useful for reducing the effects of radio frequency noise in an RFID system. A dual coil antenna is composed of two identical coils that are connected in series. The noise voltages in the two coils almost disappear when they are added because the magnitudes are equal and the polarities are opposite. The noise in an RFID reader with a dual coil antenna was 15 dB lower than that with a single coil antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.603-611
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• 2008

In this paper, we introduce a multi-coil antenna which is useful for reducing the effects of radio frequency noise in an inductively coupled RFID system. A multi-coil antenna is composed of a central coil and four subsidiary coils that are connected in series. A multi-coil antenna is designed so that the total noise disappear when the induced voltages of a central coil and subsidiary coils are added. The noise in a multi-coil antenna was about 30 dB lower than that in a single coil antenna. The multi-coil antenna is very effective in noise reduction even in an environment that the spatial distribution of RF noise is changed abruptly, and the induced noise was about 16 dB lower than that in a dual coil antenna.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1120-1124
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• 2013

Our objective of this study was to reduce radio frequency coil (RF) control time at 3 T MRI systems. A compressed method is proposed with a convex optimization and pseudo-inverse method in multi-channel RF coils. After applying the proposed methods, fields are homogenized with less field data. Even with 80% compression, the fields are well homogenized and localized, indicating that mapping requires only 20% of the original data. Detailed values are compared between each compressed result in and outside the region of interest at 3 T.

• Progress in Superconductivity and Cryogenics
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• v.20 no.1
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• pp.23-27
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• 2018

As the wireless power transfer (WPT) technology based on strongly resonance coupled method realizes large power charging without any wires through the air, there are advantages compared with the wired counterparts, such as convenient, safety and fearless transmission of power. From this reason, the WPT systems have started to be applied to the wireless charging for various power applications such as train, underwater ship, electric vehicle. This study aims for the effect and characteristics of different inserted resonance coil between Tx and Rx coils for charging system of superconducting magnetic levitation (MAGLEV) train. The transfer efficiency and effect are evaluated with helix type, rectangular type copper resonance coil, and HTS resonance coil under bulb and HTS magnet load, respectively. The input power is adapted with radio frequency (RF) power of 370 kHz below 500 W.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.7
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• pp.8-13
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• 2009

Plasma enhanced chemical vapor deposition (PECVD) is commonly used for Carbon nanotubes (CNTs) fabrication, and the process can easily be applied to industrial production lines. In this works, we developed novel magnetized radio frequency PECVD system for one line process of CNTs fabrication for charge storable electrode application. The system incorporates aspects of physical and chemical vapor deposition using capacitive coupled RF plasma and magnetic confinement coils. Using this magnetized RF-PECVD system, we firstly deposited Fe layer (about 200[nm]) on Si substrate by sputter method at the temperature of 300[$^{\circ}$] and hence prepared CNTs on the Fe catalyst layer and investigated fundamental properties by scanning electron microscopy (SEM) and Raman spectroscopy (RS). High-density, aligned CNTs can be grown on Fe/Si substrates at the temperature of 600[$^{\circ}$] or less.