• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.134-134
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• 2001

Purpose： To evaluate the physiologic background of poorly visualized aneurysms during DSA a contrast-enhanced MRA(CEMRA) due to hemodynamical isolation on clinical and experiment data. Method： Two cases of intracranial aneurysm which were poorly visualized on DSA a CEMRA and one case of intracranial aneurysm which had poor turnover of contrast mediu during DSA were selected for this clinical study. We evaluated the turnover of blood in t terminal aneurysm of handmade elastic silicon phantoms for comparative experiment. Flo experiments with DSA and contrast enhanced MRA were performed in elastic phantoms aneurysm with 3 different diameters (2, 5 and 10 mm) of neck mimicking basilar ti aneurysm, attached to pulsatile pump similar to that of human physiologic parameters. W compared the results with those of computational flow dynamics(CFD).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.7
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• pp.517-523
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• 2003

This paper presents response property of the squeeze mode type mount using Magneto-Rheological fluid (MR fluid) . The MR mount for the isolation of multi-directional vibrations was constructed in this study. Both the mechanism and shape of the mount are the same as squeeze film dampers for a rotor system. In the present work, the performance of the mount was experimentally Investigated according to the magnetic field strength. The experimental results present that the MR mount can effectively reduce the vibration in a wide range of frequency by controlling the applied electromagnetic filed strength. Viscous damping and stiffness coefficients of the MR mount tend to be changed according to the variation of the applied currents In this study.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.5
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• pp.475-483
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• 2011

A hybrid electromagnetic actuator with an air mount is designed so as to achieve the desired isolation reduce the vibration efficiency on the floor vibration. The performance specification of the hybrid electromagnetic actuator is determined based on the vibration criterion for vibration-sensitive equipment. In the design stage of the electromagnetic actuator, the simple reluctance method is adapted to analyze magnetic circuits. The result is verified by finite element analysis using ANSYS Emag. Finally, in order to confirm the design performance, a dynamic characteristic test is carried out for the prototype of a hybrid electromagnetic actuator.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1382-1390
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• 2017

This paper presents a power supply for gate drivers, which uses a magnetic resonance wireless power transfer system. Unlike other methods where multiple antennas are used to supply power for the gate drivers, the proposed method uses a single antenna in an insulated receiver to make multiple mutually isolated power supplies. The power transmitted via single antenna is distributed to multiple power supplies for gate drivers through resonant capacitors connected in parallel that also block DC bias. This approach has many advantages over other methods, where each gate driver needs to be supplied with power using multiple receiver antennas. The proposed method will therefore lead to a reduction in production costs and circuit area. Because the proposed circuit uses a high resonance frequency of 6.78 MHz, it is possible to implement a transmitter and a receiver using a small-sized spiral printed-circuit-board-type antenna. This paper used a single phase-leg circuit configuration to experimentally verify the performance characteristics of the proposed method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.86-89
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• 1994

This paper describes the fabrication and basic characteristics of a Si Hall device fabricated on a SOI(Si-on-insulator) structure. In which SOI structure was formed by SOB(Si-wafer direct bonding) technology and the insulator of the SOI structure was used as the dielectrical isolation layer of a Hall device. The Hall voltage and sensitivity of the implemented SDB SOI Hall devices showed good linearity with respectivity to the applied magnetic flux density and supple iud current. The product sensitivity of the SDB SOI Hall device was average 670 V/A$.$T and its value has been increased up to 3 times compared to that of bulk Si with buried layer of 10$\mu\textrm{m}$. Moreover, this device can be used at high-temperature, high-radiation and in corrosive environments.

• Journal of the Korean Chemical Society
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• v.62 no.3
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• pp.187-190
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• 2018

A three-component coupling reaction of phenylacetylene, p-toluenesulfonyl azide, and water through copper catalysis is described to provide knowledge of spectroscopy and catalytic reactions and to introduce current research topics in organic chemistry for second-year undergraduate students. In the presence of stoichiometric amounts of phenylacetylene, p-toluenesulfonyl azide, and triethylamine, the reaction was performed with 4 mol% CuCl in water as the sole solvent and was completed in 1.5 h. A practical purification method and recrystallization of the crude reaction mixture resulted in the rapid isolation of the desired product with yields of 42~65%. Students characterized 4-methyl-N-(phenylacetyl)benzenesulfonamide by using melting-point determination, infrared spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. This experimental procedure and spectroscopic data analysis will serve as a platform for students to apply classroom knowledge in practical state-of-the-art research.

• Natural Product Sciences
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• v.22 no.1
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• pp.41-45
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• 2016

Extraction and fractionation of Pulsatilla koreana flowers followed by, repeated open column chromatography for EtOAc and n-BuOH fractions yielded four flavonoid glycosides, namely, astragalin (1), tiliroside (2), buddlenoide A (3), and apigenin-7-O-(3"-E-p-coumaroyl)-glucopyranoside (4). The chemical structures of these flavonoid glycosides were elucidated on the basis of various spectroscopic methods including electronic ionization mass spectrometry (EI-MS), 1D NMR ($^1H$, $^{13}C$, DEPT), 2D NMR (gCOSY, gHSQC, gHMBC), and infrared (IR) spectrometry. This study represents the first report of the isolation of the flavonoid glycosides from the flowers of P. koreana.

• Progress in Superconductivity and Cryogenics
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• v.25 no.1
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• pp.1-5
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• 2023

The study of two-dimensional electron systems with extraordinarily low levels of disorder was, for a long time, the exclusive privilege of the epitaxial thin film research community. However, the successful isolation of graphene by mechanical exfoliation has truly disrupted this field. Furthermore, the assembly of heterostructures consisting of several layers of different 2D materials in arbitrary order by exploiting van der Waals forces has been a game-changer in the field of low-dimensional physics. This technique can be generalized to the large class of strictly 2D materials and offers unprecedented parameters to play with in order to tune electronic and other properties. It has led to a paradigm shift in the field of 2D condensed matter physics with bright prospects. In this review article, we discuss three device fabrication techniques towards high mobility devices: suspended structures, dry transfer, and pick-up transfer methods. We also address state-of-the-art device structures, which are fabricated by the van der Waals pick-up transfer method. Finally, we briefly introduce correlated ground states in the fractional quantum Hall regime.

• Journal of Astronomy and Space Sciences
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• v.24 no.4
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• pp.397-408
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• 2007

Diplexer is one of core devices needed to communicate with satellite using single ground antenna by separating uplink and downlink signal. This paper presents the design of the S-band diplexer for LEO TT&C application, especially for KOMPSAT (KOrea Multi-Purpose SATellite). To cope with requirements such as high handling power, low insertion loss, air-cavity resonator with high quality factor was considered as one of design drivers. Design was started with predicting unloaded Q and equivalent circuit from the structure of air-cavity resonator. For the convenience of adjustment, the coupling factor placed between resonators was estimated from COTSEM (Electro-Magnetic) simulator, EESOF $ADS^{TM}$, and expressed with 2-order polynomial regression. To improve the isolation between transmitting part (Tx) and receiving part (Rx), the inductive and capacitive attenuation poles were inserted between $4^{th}\;and\;6^{th}$ resonator respectively. The fabricated diplexer consists of two bandpass filters and each filter has eight resonants. From the measurement, it was shown that major requirements such as 0.5dB of insertion loss, 20dB of return loss and 100dB of isolation were fully satisfied within passband.

• Food Science and Biotechnology
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• v.17 no.6
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• pp.1214-1220
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• 2008

Secondary metabolites from the fruit body of Phellinus linteus were evaluated for their proliferative effect on human osteoblast-like cells. 3-[4,5-Dimethylthiazole-2-y1]-2,5-diphenyl-tetraxolium bromide (MTT) assay and alkaline phosphatase (ALP) activity assay were used to assess the effect those isolates on the human osteoblast-like cell line (Saos-2). Activity-guided fractionation led to the isolation of ALP-activating phenolic compounds through the extraction of P. linteus, solvent partitioning, and repeated silica gel and octadecyl silica gel (ODS) column chromatographic separations. From the result of spectroscopic data including nuclear magnetic resonance (NMR), mass spectrometry (MS), and infrared spectroscopy (IR), the chemical structures of the compounds were determined as 4-(4-hydroxyphenyl)-3-buten-2-one(1), 2-(3',4'-dihydroxyphenyl)-1,3-benzodioxole-5-aldehyde (2), 4-(3,4-dihydroxyphenyl)-3-buten-2-one (3), 3,4-dihydroxybenzaldehyde (4), and protocatechuic acid methyl ester (5), respectively. This study reports the first isolation of compounds 1-3 and 5 from P. linteus. In addition, all phenolic compounds stimulated proliferation of the osteoblast-like cells and increased their ALP activity in a dose-dependent manner ($10^{-8}$ to $10^{-1}\;mg/mL$). The present data demonstrate that phenolic compounds in P. linteus stimulated mineralization in bone formation caused by osteoporosis. The bone-formation effect of P. linteus seems to be mediated, at least partly, by the stimulating effect of the phenolic compounds on the growth of osteoblasts.