• 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.

• Journal of the Korean Magnetic Resonance Society
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• v.7 no.1
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• pp.25-36
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• 2003

The performance of radio frequency (RF) coils, used in MRI units, is determined by the image uniformity and the signal-to-noise ratio (SNR). Birdcage and surface coils are commonly used. A birdcage coil provides a good image uniformity while a surface coil produces a high SNR. In this study, therefore, a staircase coil was designed from a standard version of a birdcage coil, with some structural changes to increase SNR while maintaining image uniformity. In phantom experiments, the improvement of the image to uniformity and the SNR increase of the staircase coil compared with the values for the birdcage coil were about 3.5% and 35%, respectively. In clinical experiment, the SNR increase of the staircase coil, compared with the value for the birdcage coil was about 40% in bone, muscle and blood-vessel tissues. These results show that the performance of the staircase coil was very improved over the standard birdcage coil in terms of SNR, and that image uniformity was maintained. Therefore, the staircase coil designed by this study should be useful in experimental and clinical l.5T MRI systems, and this coil offers an alternative method of quadrature detection.

• Investigative Magnetic Resonance Imaging
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• v.18 no.1
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• pp.52-58
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• 2014

Purpose : To establish a pH measurement system for a mouse tumor study using a clinical scanner, to develop the $^1H$ and 31P radio frequency (RF) coil system and to test pH accuracy with phantoms. Materials and Methods: The $^1H$ and the $^{31}P$ surface coils were designed to acquire signals from mouse tumors. Two coils were positioned orthogonally for geometric decoupling. The pH values of various pH phantoms were calculated using the $^1H$ decoupled $^{31}P$ MR spectrum with the Henderson-Hasselbalch equation. The calculated pH value was compared to that of a pH meter. Results: The mutual coil coupling was shown in a standard $S_{12}$. Coil coupling ($S_{12}$) were -73.0 and -62.3 dB respectively. The signal-to-noise ratio (SNR) obtained from the homogeneous phantom $^1H$ image was greater than 300. The high resolution in vivo mice images were acquired using a $^{31}P$-decoupled $^1H$ coil. The pH values calculated from the $^1H$-decoupled $^{31}P$ spectrum correlated well with the values measured by pH meter ($R^2$=0.97). Conclusion: Accurate pH values can be acquired using a $^1H$-decoupled $^{31}P$ RF coil with a clinical scanner. This two-surface coil system could be applied to other nuclear MRS or MRI.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.1
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• pp.96-100
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• 2012

In high static field magnetic resonance imaging(MRI) systems, $B_0$ fields of 7 T and 9.4 T, the impressed RF field shows larger inhomogeneity than in clinical MRI systems with B0 fields of 1.5 T and 3.0 T. In multi-channel RF coils, the magnitude and phase of the input to each coil element can be controlled independently to reduce the non-uniformity of the impressed RF $B_1^+$ field. The convex optimization technique has been used to obtain the optimum excitation parameters with iterative solutions for homogeneity in a selected ROI(Region of Interest). To demonstrate the technique, the multichannel transmission line coil was modeled together with a human head phantom at 400 MHz for the 9.4 T MRI system and $B_1^+$ fields are obtained. In this paper, all the optimized $B_1^+$ in each isolated ROIs are combined to achieve significantly improved homogeneity over the entire field of view. The simulation results for 9.4 T MRI systems are discussed in detail.

• Progress in Superconductivity and Cryogenics
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• v.16 no.3
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• pp.21-25
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• 2014

As wireless power transfer (WPT) technology using strongly coupled electromagnetic resonators is a recently explored technique to realize the large power delivery and storage without any cable or wire, this technique is required for diffusion of electric vehicles (EVs) since it makes possible a convenient charging system. Typically, since the normal conducting coils are used as a transmitting coil in the CPT system, there is limited to deliver the large power promptly in the contactless EV charging system. From this reason, we proposed the combination CPT technology with HTS transmitting antenna, it is called as, superconducting contactless power transfer for EV (SUWPT4EV) system. As the HTS coil has an enough current density, it can deliver a mass amount of electric energy in spite of a small scale antenna. The SUCPT4EV system has been expected as a noble option to improve the transfer efficiency of large electric power. Such a system consists of two resonator coils; HTS transmitting antenna (Tx) coil and normal conducting receiver (Rx) coil. Especially, the impedance matching for each resonator is a sensitive and plays an important role to improve transfer efficiency as well as delivery distance. In this study, we examined the improvement of transmission efficiency and properties for HTS and copper antennas, respectively, within 45 cm distance. Thus, we obtained improved transfer efficiency with HTS antenna over 15% compared with copper antenna. In addition, we achieved effective impedance matching conditions between HTS antenna and copper receiver at radio frequency (RF) power of 370 kHz.