• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.79-80
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• 2005

The solid precursor produced by the dehydration of the gel at $120^{\circ}C$ for 12h is not in the amorphous state as expected but in a crystalline state. X-ray diffraction peaks of nearly the same angular position as the peaks of high Tc phase were observed in the precursor. Experimental results suggest that the intermediate phase formed before the formation of the superconducting phase may be the most important fact in determining whether it is easy to form the superconducting phase or not, because the nucleation barriers of the two superconducting phase may be altered by the variation of the crystal structures of those intermediate phase.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.11
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• pp.548-556
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• 2003

Switched reluctance motor(SRM) has simple magnetic structure, and needs simple power electronic driving circuit. It is very useful for wide range adjustable speed drive system. But, SRM drive generates large vibration and acoustic noise because it is commutated individually by step pulse m.m.f of each phase. In the vibration and acoustic noise characteristics. the considerable vibration and noise is induced by radial deforming of stator, so the frequency of dominant vibration and noise is coincident with the frequency of natural frequency of mechanical structure. This radial vibration force is generated by abrupt change of radial magnetic force in the phase commutation region. This paper studied about simple electromagnetic structure of SRM using auxiliary compensating winding for the reduction of noise and vibration. This auxiliary winding is coupled with all phase windings electromagnetically and absorb and transfer magnetic energy variation from phase to other phase. By this interaction of phase windings and compensating winding can reduce abrupt radial force change and vibration and acoustic noise. In this paper the improvement effect is examined by the test of prototype machine.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1966-1967
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• 2005

The solid precursor produced by the dehydration of the gel at $120^{\circ}C$ for 12h is not in the amorphous state as expected but in a crystalline state. X-ray diffraction peaks of nearly the same angular position as the peaks of high Tc phase were observed in the precursor. Experimental results suggest that the intermediate phase formed before the formation of the superconducting phase may be the most important fact in determining whether it is easy to form the superconducting phase or not, because the nucleation barriers of the two superconducting phase may be altered by the variation of the crystal structures of those intermediate phase.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.379-382
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• 2017

This paper proposes a $4{\times}4$ broadband phased array antenna using a Left-Handed Transmission Line (LHTL) based phase shifter. The phased array is constructed with sixteen quasi-Yagi antenna elements and the phase shifters, as well as four power dividers. A key component of the system, the LHTL based phase shifter is able to control a phase delay of incident waves linearly and continuously. The fabricated phased array antenna operate for a frequency range of 800 MHz (1.6 GHz~2.4 GHz). The beam scanning range of the $4{\times}4$ array antenna is ${\pm}27^{\circ}$ horizontally and vertically while the antenna gain is maintained with a variation of ${\pm}1.4dBi$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.8
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• pp.55-62
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• 2015

This paper deals with a switching method to minimize the current ripple component of 3-phase interleaved bidirectional DC-DC converter for charging and discharging of the battery. The characteristics of the output current ripple in 3-phase and 2-phase operation modes according to the variation of battery voltage is analyzed and a phase conversion method for minimizing the magnitude of the current ripple is proposed. The proposed method can extend the light load range because the switching frequency is lower than that of a 3-phase operating system. Simulation and experimental results show the usefulness of the proposed method.

• Journal of Magnetics
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• v.20 no.1
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• pp.91-96
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• 2015

As many researchers are relentlessly trying to improve the power generation schemes from the power grid, to meet the constantly increasing electricity demand. In this paper, the results of a finite element analysis are carried out to study on a design optimization of an asymmetric air-gap structure in 3-phase Permanent Magnet Brushless DC Motors. To achieve a high efficiency for a 3-phase PM BLDC motor, the asymmetric air-gap structure is proposed considering the rotation direction of a motor. Generally, a single-phase BLDC motor is applied asymmetric air-gap structure for starting. This is because the asymmetric air-gap structure causes reluctance variation so the motor can utilize reluctance torque toward a rotation direction. In this paper, the asymmetric air-gap is applied to 3-phase BLDC SPM motor so it utilizes reluctance torque with alignment torque. A proposed model is designed by 2-D FE analysis and the results are verified by experimental test.

• Journal of Life Science
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• v.19 no.12
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• pp.1698-1704
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• 2009

Gemcitabine is an anticancer drug used to treat a variety of solid tumors. The drug is rapidly inactivated by cytidine deaminase in plasma and its hydrophilicity restricts the extent of quantification that is possible using reversed-phase liquid chromatography. In this paper, we report a rapid and precise method to analyze velocity and peak efficiency using ultra-performance liquid chromatography (UPLC) with a reversed-phase column. The retention periods of gemcitabine and 2'-deoxycytidine at 283 nm were 3.2 and 2.1 min, respectively. The assay provided highly linear results in the range of $0.1{\sim}20{\mu}g/ml$ ($r^2$ > 0.999). The coefficients of variation of the intra-day and inter-day assays were less than 10.0%. We observed that the estimated average concentrations of the intra-day and inter-day assays ranged from 97.3 to 113.5% to verify the accuracy. These results suggest that this new reversed-phase UPLC method is a rapid and reliable way of determining gemcitabine levels.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.470-480
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• 2011

Analog ferrite phase shifters based on rectangular waveguides which are used as component of passive phased array system have high power handling capability, but it is heavy and has high cost to fabricate. In this paper, we propose an analog ferrite phase shifter using substrate integrated waveguide(SIW), which has low cost and is easy to fabricate because it uses printed circuit board(PCB) process. The proposed structure is fabricated by using centeral dielectric material removal for inserting a ferrite bar. The measured results show that the proposed structure has not only $5.1^{\circ}$/mm phase variation but also return loss variation under 12.9 dB. Therefore, it is expected that the proposed phase shifter can plays an role to reduce weight and to has low cost on the phased array system.

• Toxicological Research
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• v.13 no.4
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• pp.377-383
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• 1997

To investigate the circadian variation in the bromobenzene metabolism, bromobenzene(400 mg/kg body weight) was intraperitoneally administered to the rats every other day for 6 days both in the night; 24:00 and the day; 12:00. Each group of animals was sacrificed at 8hr after last injection of bromobenzene. The contents of hepatic CYP were more increased in control rats of night phase than those of day phase but in case of bromobenzene treatment there were no differences in hepatic CYP between rats of the night phase and those of day phase and the injection of prednisolon inhibited the hepatic CYP content in rats. Furthermore, the decreasing rate of hepatic glutathione contents to the control was higher in rats of day phase than those of night phase by the bromobenzene treatment. And the hepatic glutathione S-transferase activities were increased both in control and bromobenzene treated rats of the night phase than those of day phase. On the other hand, liver weight per body weight(%), hepatic lipid peroxide content, serum levels of alanine aminotransferase were more increased both in bromobenzene-treated and control rats of the night phase than those in the day phase. These results indicate that the rats of night phase may induce more accelerated formation of bromobenzene 3,4-oxide from bromobezene than those of day phase in rats.

• ETRI Journal
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• v.36 no.2
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• pp.321-324
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• 2014

This letter describes a two-phase clock oxide thin-film transistor shift register that executes a robust operation over a wide threshold voltage range and clock coupling noises. The proposed circuit employs an additional Q generation block to avoid the clock coupling noise effects. A SMART-SPICE simulation shows that the stable shift register operation is established for the clock coupling noises and the threshold voltage variation from -4 V to 5 V at a line time of $5{\mu}s$. The magnitude of coupling noises on the Q(15) node and Qb(15) node of the 15th stage is respectively -12.6 dB and -26.1 dB at 100 kHz in the proposed circuit, compared to 6.8 dB and 10.9 dB in a conventional one. In addition, the estimated power consumption is 1.74 mW for the proposed 16-stage shift registers at $V_{TH}=-1.56V$, compared to 11.5 mW for the conventional circuits.