• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.4
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• pp.35-45
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• 2008

This paper present the Three-Level converter using IM(Integrated Magnetics) method for high power application. In power conversion system, magnetic components are important devices used for energy storage, energy transfer, galvanic isolation and filtering. The proposed Three-Level converter is to reduce the number of magnetic components using transformer integrated with output inductor. This paper proposes reluctance model base on the magnetic analysis for the Three-Level converter. Also, the secondary rectification was discussed by a single core transformer winding. A protype featuring 540[V] input, 48[V] output, 40[kHz] switching frequency, and 3[kW] output power using IGBT.

• Korean Journal of Food Science and Technology
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• v.31 no.5
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• pp.1386-1391
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• 1999

The methanol extract of Gardenia jasminoides Ellis showed antimicrobial activity against bacteria and yeasts. The extract was successively purified with solvent fractionation, silica gel adsorption column chromatography, Sephadex LH-20 column chromatography, octadecylsilane column chromatography. The purified active substance was isolated by high performance liquid chromatography. The isolated compound was 3,4-dihydroxybenzoic acid which was determined by mass spectrometer, gas chromatograph-mass spectrometer, $^{1}H-nuclear$ magnetic resonance, $^{13}C-nuclear$ magnetic resonance and two-dimensional nuclear magnetic resonance. The content of 3,4-dihydroxybenzoic acid was $32.7\;{\mu}g/g$ in dried fruits of Gardenia jasminoides Ellis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.5 s.248
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• pp.550-559
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• 2006

This paper presents designs and performance investigations of two bypass-type MR (magneto-rheological) shock dampers for high impulsive force systems, one of which is with single rod and the other with double rod. First of all, on the basis of the Bingham properties of the MR fluid and the magnetic field analysis of the magnetic circuit, the MR shock dampers are designed and manufactured. After experimental investigations on their magnetic field-dependent damping forces and responses characteristics, dynamic models of the proposed dampers are formulated and compared. Then, a simple 1 degree-of-freedom mass-drop system is constructed, and the effective and practical control algorithm is designed by considering dynamic characteristics of the shock control system. The shock control performances of the proposed MR shock dampers are verified through the comparison study of experiment results with simulation ones.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.91-98
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• 2004

TFLIM(Transverse Flux Linear Induction Motor), making its closed magnetic path with the direction of the traveling field orthogonal, had been developed to decrease an edge effect of the general induction motor. To control the levitation force and the thrust force on the secondary part of TFLIM independently, the various methodologies have been presented. When we try to achieve the independent control using only the multi-phase inputs assigned in the stator coils as an approach, in which condition we can minimize the coupling effect between two forces\ulcorner In this paper, we show the qualitative influence of a slip frequency, an ac magnitude, a dc offset superposed in the ac power, and a major parameter of TFLIM on the couple through the computer simulation. And to realize the independent motions between levitation and thrust motion without any auxiliary means fur isolation of the secondary part of TFLIM, the decouple compensator is suggested, including the experimental results.

• Journal of Applied Biological Chemistry
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• v.63 no.4
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• pp.319-325
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• 2020

The liquids of Lycopersicon esculentum were extracted with 70% aqueous MeOH and the concentrates were partitioned into EtOAc, n-BuOH, and H2O fractions. The repeated silica gel and octadecyl silica gel column chromatographies for the EtOAc fraction, whose activity was confirmed, led to isolation of one flavonol compound. The chemical structures of the compound were determined as quercetin (1) based on spectroscopic analyses including nuclear magnetic resornance, infrarad spectroscopy, and mass spectroscopy. Through this study, the antioxidant efficacy was confirmed by demonstrating that the L. esculentum fraction showing an increase in glutathione mean (GM) and a decrease in glutathione heterogeneity (GH) uniformly raises the intracellular glutathione (GSH) level.

• Journal of Biomedical Engineering Research
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• v.27 no.1
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• pp.30-37
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• 2006

Injecting currents into an electrically conducting subject, we may measure the induced magnetic flux density distributions using an MRI scanner. The measured data are utilized to reconstruct cross-sectional images of internal conductivity and current density distributions in Magnetic Resonance Electrical Impedance Tomography (MREIT). Injection currents are usually provided in a form of mono-polar or bi-polar pulses synchronized with an MR pulse sequence. Given an MRI scanner performing the MR phase imaging to extract the induced magnetic flux density data, the current source becomes one of the key parts determining the signal-to-noise ratio (SNR) of the measured data. Since this SNR is crucial in determining the quality of reconstructed MREIT images, special care must be given in the design and implementation of the current source. This paper describes a current source design for MREIT with features including interleaved current injection, arbitrary current waveform, electrode switching to discharge any stored charge from previous current injections, optical isolation from an MR spectrometer and PC, precise current injection timing control synchronized with any MR pulse sequence, and versatile PC control program. The performance of the current source was verified using a 3T MRI scanner and saline phantoms.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.10
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• pp.869-875
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• 2015

In this paper, the surface wave that caused the isolation problem when the design of the array antenna is studied. The grounded dielectric slab model is used in order to simulate in the similar environment with the surface wave of the microstrip patch antenna. The propagation of the surface wave on the various types of grounds which are defected ground structure(DGS), perfect magnetic conductor(PMC), Soft-surface, and Hard-surface is simulated. As a result, 25 % power is blocked by the DGS when the TM-wave incident. Also, 95 % power is blocked by the PMC and Soft-surface. This study will be very useful to increase the gain of an array antenna by improving the isolation between the antenna elements.

• Journal of the Korean Magnetic Resonance Society
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• v.19 no.2
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• pp.67-73
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• 2015

The microcystin is a cyclic heptapeptide from metabolites of cyanobacteria in the genera mycrocystis, anabaeba as a result of eutrophication. It has been known that microcystin-LR is a potent inhibitor of the catalytic subunits of protein phosphatase-1 (PP-1) as well as powerful tumor promoter. The active site of microcystin actually has two metal ions $Fe^{2+}/Zn^{2+}$ close to the nucleophilic portion of PP-1-microcystin complex. We report the isolation and purification of this microcystin-LR from cyanobacteria (blue-green algae) obtained from Daechung Dam in Chung-cheong Do, Korea. Microcystin-LR was extracted from solid-phase extraction (SPE) sample preparation using a CN cartridge. The cyanobacteria extract was purified to obtain microcystin-LR by HPLC method and identified by LC/MS. The detail structural studies that can elucidate the possible role of monovalent and divalent metal ions in PP-1-microcystin complexation were carried out by utilizing molecular dynamics. Conformational changes in metal binding for ligands were monitored by molecular dynamic computation and potential of mean force (PMF) using the method of the free energy perturbation. The microcystin-metal binding PMF simulation results exhibit that microcystin can have very stable binding free energy of -10.95 kcal/mol by adopting the $Mg^{2+}$ ion at broad geometrical distribution of $0.5{\sim}4.5{\AA}$, and show that the $K^+$ ion can form a stable metal complex rather than other monovalent alkali metal ions.

• Journal of Korean Foot and Ankle Society
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• v.18 no.3
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• pp.100-107
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• 2014

Purpose: The purpose of this study is to evaluate the efficacy of mesenchymal stem cell (MSC) isolation by the magnetic-activated cell sorting (MACS) method in tendon tissue-derived cells compared to the colony picking method for isolation of MSCs by picking colony-forming cells. Materials and Methods: Human tendon-derived cells were isolated by enzyme digestion using normal tendon tissues from three donors. We used the magnetic kit and well-known MSC markers (CD90 or CD105) to isolate MSCs in tendon-derived cells using MACS. Cloning cylinders were used to isolate colony-forming cells having MSC characteristics in tendon-derived cells. Colony-forming unit-fibroblast (CFU-F) assay was used to evaluate the self-renewal capacity of cells isolated using the colony picking method or MACS. For comparison of differentiation potentials into osteogenic or adipogenic lineage between two groups, alizarin red S and oil red O staining were performed at 14 days after induction of differentiation in vitro. Results: Flow cytometry results showed that early passage tendon-derived cells expressed CD44 in 99.13%, CD90 in 56.51%, and CD105 in 86.19%. In the CFU-F assay, CD90+ or CD105+ cells isolated with MACS showed larger colony formation in size than cells isolated using the colony picking method. We also observed that CD90+ or CD105+ cells were constantly differentiated into both osteogenic and adipogenic lineages in cells from all donors, whereas cells isolated using the colony picking method were heterogeneous in differentiation potentials to the osteogenic and adipogenic lineages. Conclusion: CD90+ or CD105+ cells isolated using MACS showed superior MSC characteristics in the self-renewal and multi-differentiation capacities compared with cells isolated using the colony picking method.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.1
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• pp.17-22
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• 2000

A quaternary alloy film of $CoCr_{16.2}Pt_{10.8}Ta_4$was investigated for its magnetic properties and c-axis orientation with and without Ti underlayer. Additional elements such as Ta, Pt have been frequently introduced in CoCr alloy film for perpendicular recording as a means of improving magnetic performance. It has been reported that the addition of Pt and Ta in CoCr increase the coercivity and the magnetic isolation of columnar grains, respectively. However, CoCrPtTa perpendicular magnetic layer should be more increased its perpendicular magnetic anisotropy than at present for the application of ultrahigh recording density. The improvement of underlayers and substrate materials is one of the promised schemes to intensify the perpendicular magnetic anisotropy. In this study, the insertion of Ti underlayer shows the remarkable improvement of c-axis orientation compare with the direct deposition on the bare glass. The mechanism about this effect of Ti underlayer on CoCrPtTa is not to be clarified yet. Meanwhile, it is found that the magnetic domain of CoCrPtTa on 20 nm Ti underlayer has the continuous stripe pattern but the one of CoCrPtTa on 90 nm Ti underlayer shows the discrete mass type from the results of MFM investigation. This phenomenon is to be a distinct evidence that the improvement of perpendicular anisotropy by the adoption of Ti underlayer is originated from the reinforcement of the grain boundary segregation in CoCrPtTa alloy. Moreover, the transition of the M-H hysteresis pattern with the thickness of Ti underlayer indicates that the major contribution of Ti underlayer is not the magnetocrystalline anisotropy but the shape anisotropy due to the formation of uniform columnar grains by the nonmagnetic alloy segregation.