• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.6
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• pp.592-601
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• 2004

The performance of active power filter depends on the inverter characteristic, the control method, and the accuracy of reference signal generator. The accuracy of reference signal generator is the most critical item to determine the performance of active power filter. This paper introduces a novel reference signal generator composed of improved adaptive predictive filter. The performance of proposed reference signal generator was verified by means of simulation with MATLAB. The application feasibility was evaluated by building and experimenting a single-phase active power filter based on the proposed reference generator, which was implemented in the DSP(digital signal processor) TMS320C31. Both simulation and experimental results confirm that the proposed reference signal generator can be utilized for the active power filter.

• YAKHAK HOEJI
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• v.52 no.1
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• pp.12-19
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• 2008

The organic acids (formic acid, acetic acid and propionic acid), phenol and benzopyrene in wood vinegar were determine by HPLC. An $Atlantis^{TM}dC_{18}$ column with a acetonitrile: 0.1% phosphoric acid (5: 95, organic acids), acetonitrile: water (10 : 90, phenol), 100% acetonitrile (benzopyrene) as a mobile phase was used. Retention time of acetic acid, formic acid, propionic acid, phenol and benzopyrene was 4.77, 3.73, 9.08, 30.97 and 6.10 min, respectively. The calibration curves of organic acids, phenol, benzopyrene were linear over the concentration range of $30{\sim}500,\;60{\sim}1000$, and $3{\sim}50\;{\mu}g/ml$ with correlation coefficient of above 0.999. The limit of detection (LOD) and limit of quantitation (LOQ) of acetic acid, formic acid, propionic acid, phenol, and benzopyrene was 1.71 and 5.19, 1.11 and 3.35, 4.87 and 14.74, 6.45 and 19.55, 0.08 and $0.24\;{\mu}g/ml$, respectively. The coefficients of variation for intra- and inter-day assay were $0.21{\sim}4.14$ and $0.07{\sim}1.19%$, respectively and the precision was $95{\sim}115%$. From this study, we suggest that HPLC is suitable method for the determination of organics in wood vinegar and could be applied to quality control of wood vinegar.

• Proceedings of the KSRS Conference
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• v.1
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• pp.21-24
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• 2006

Processes controlling the interannual variation of mixed layer temperature (MLT) averaged over the NINO3 domain ($150-90^{\circ}W$, $5^{\circ}N-5^{\circ}S$) are studied using an ocean data assimilation product that covers the period of 1993 to 2003. Advective tendencies are estimated here as the temperature fluxes through the domain's boundaries, with the boundary temperature referenced to the domain-averaged temperature to remove the dependence on temperature scale. The overall balance is such that surface heat flux opposes the MLT change but horizontal advection and subsurface processes assist the change. The zonal advective tendency is caused primarily by large-scale advection of warm-pool water through the western boundary of the domain. The meridional advective tendency is contributed mostly by Ekman current advecting large-scale temperature anomalies though the southern boundary of the domain. Unlike many previous studies, we explicitly evaluate the subsurface processes that consist of vertical mixing and entrainment. In particular, a rigorous method to estimate entrainment allows an exact budget closure. The vertical mixing across the mixed layer (ML) base has a contribution in phase with the MLT change. The entrainment tendency due to temporal change in ML depth is negligible comparing to other subsurface processes. The entrainment tendency by vertical advection across the ML base is dominated by large-scale changes in wind-driven upwelling and temperature of upwelling water. Tropical instability waves (TIWs) result in smaller-scale vertical advection that warms the domain during La Ni? cooling events. When the advective tendencies are evaluated by spatially averaging the conventional local advective tendencies of temperature, the apparent effects of currents with spatial scales smaller than the domain (such as TIWs) become very important as they redistribute heat within the NINO3 domain. However, such internal redistribution of heat does not represent external processes that control the domain-averaged MLT.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.31-39
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• 2007

To perform on-line cyber education, it is indispensable to delivery contents file to participant users. When users' requests occur simultaneously in a shot period, server falls into overload phase. A common to avoid overload is a software solution based on P2P, which does no cost any additional expense. But, in this solution, it yields many problems such as service delay and system failure because of peer self-control. In this paper we propose an efficient load balancing policy based on P2P system. which is the contents delivery system for cyber education system using idle computing power in the proposed solution, we present server selection scheme called P2P-Pattern method, which results in minimum service delay. we can see that our scheme outperforms previous scheme.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.12
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• pp.68-74
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• 2010

A sub-${\mu}$W CMOS Wien-Bridge oscillator for ultra low power (ULP) radio applications is presented. The Wien-Bridge oscillator is based on an non-inverting opamp amplifier with a closed-loop gain $1+R_2/R_1$ as a means of providing necessary loop gain. An additional RC network provides appropriate phase shift for satisfying the Barkhausen oscillation condition at the given frequency of 1/($2{\pi}RC$). In this design, we propose a novel loop gain control method based on a variable capacitor network instead of a rather conventional variable resistor network. Implemented in $0.18{\mu}m$ CMOS, the oscillator consumes only 560 nA at the oscillation frequency of 22 kHz.

• Bulletin of the Korean Chemical Society
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• v.28 no.7
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• pp.1187-1194
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• 2007

The three major active isoflavonoids (calycosin-7-O-β -glucoside, isomucronulatol 7-O-β-glucoside, formononetin) and two main saponins (astragaloside I, astragaloside IV) in an extract of Radix Astragali were determined using rapid, sensitive, reliable HPLC/UV and LC-ESI-MS/MS methods. The separation conditions employed for HPLC/UV were optimized using a phenyl-hexyl column (4.6 × 150 mm, 5 μm) with the gradient elution of acetonitrile and water as the mobile phase at a flow rate of 1.0 mL/min and a detection wavelength of 230 nm. The specificity of the peaks was determined using a triple quadrupole tandem mass spectrometer equipped with an electrospray ionization (ESI) source that was operated in multiple reaction monitoring (MRM) in the positive mode. These methods were fully validated with respect to the linearity, accuracy, precision, recovery and robustness. The HPLC/UV method was applied successfully to the quantification of three major isoflavonoids in the extract of Radix Astragali. The results indicate that the established HPLC/UV and LC-ESI-MS/MS methods are suitable for the quantitative analysis and quality control of multi-components in Radix Astragali.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.101-108
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• 2013

In this paper, we propose a method in which the negative acknowledge (NACK) message is used as command for cooperation and spectrum sharing. This allows for an automatic request for cooperation and sharing when the direct link of the primary user is in outage, and also allows for saving the number of control messages in cooperation-spectrum sharing based paradigm. In the sharing phase, the selected relay shares a power fraction of $1-{\alpha}$ for secondary transmitted signal while the remaining of ${\alpha}$ is for primary retransmitted signal. In the case of no relay collected, primary transmitter uses NACK as a command to retransmit the signal with fully power fraction (${\alpha}=1$). Both systems are assumed to employ BPSK signals. In this scheme, we propose the joint optimal decoding in the secondary user. The frame error rate (FER) performance at both systems is then analyzed. The theoretical and simulation results validate the analysis and confirm the efficiency of the protocol.

• Korean Journal of Oriental Medicine
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• v.18 no.1
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• pp.85-92
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• 2012

Objective : The purpose of this study was to investigate the anti-cancer effects of Sophorae Radix and the effects of 5-Fluorouracil (5-FU) in human gastric adenocarcinoma cells (AGS). Method : We used human gastric adenocarcinoma cell line, AGS cells. We examined cell death by MTT assay and caspase 3 assay with Sophorae Radix. To examine the inhibitory effects of Sophorae Radix, cell cycle (sub G1) analysis was done the AGS cells after three days with Sophorae Radix. The reversibility of Sophorae Radix was examined on one day to five days treatment with 100 ${\mu}g/ml$ Sophorae Radix. Result : Sophorae Radix inhibited the growth of AGS cells in a dose-dependent fashion. Also we showed that Sophorae Radix induced apoptosis in AGS cells by MTT assay, caspase 3 assay and sub-G1 analysis. Sophorae Radix combined with 5-FU markedly inhibited the growth of AGS cells compared to Sophorae Radix or 5-FU alone. After 3 days treatment of AGS cells with Sophorae Radix, the fraction of cells in sub-G1 phase was much higher than that of the control group. Conclusion : Our findings provide insight into unraveling the effects of Sophorae Radix in human gastric adenocarcinoma cells and developing therapeutic agents against gastric cancer.

• Korean Journal of Oriental Medicine
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• v.18 no.1
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• pp.75-84
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• 2012

Objective : The purpose of this study was to investigate the anti-cancer effects of Sophorae Radix and the effects of Doxorubicin (DOX) in human breast adenocarcinoma cells (MCF-7). Method : We used human breast adenocarcinoma cell line, MCF-7 cells. We examined cell death by MTT assay and caspase 3 assay with Sophorae Radix. To examine the inhibitory effects of Sophorae Radix, cell cycle analysis was done the MCF-7 cells after three days with Sophorae Radix. The reversibility of Sophorae Radix was examined on one day to five days treatment with 100 ${\mu}g/ml$ Sophorae Radix. Result : Sophorae Radix inhibited the growth of MCF-7 cells in a dose-dependent fashion. Also we showed that Sophorae Radix induced apoptosis in MCF-7 cells by MTT assay, caspase 3 assay and sub-G1 analysis. Sophorae Radix combined with DOX markedly inhibited the growth of MCF-7 cells compared to Sophorae Radix or DOX alone. After 3 days treatment of MCF-7 cells with Sophorae Radix, the fraction of cells in sub-G1 phase was much higher than that of the control group. Conclusion : Our findings provide insight into unraveling the effects of Sophorae Radix in human breast adenocarcinoma cells and developing therapeutic agents against breast cancer.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.6
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• pp.490-497
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• 2008

For continuous operation of the sulfur-iodine(SI) thermochemical cycle, which is expected practical method for massive hydrogen production, suggesting operation conditions at steady state is very important. Especially, in the Bunsen reaction section, the Bunsen reaction as well as side reactions is occurring simultaneously. Therefore, we studied on the relation between the variation of compositions in product solution and side reactions. The experiments for Bunsen reaction were carried out in the temperature range, from 268 to 353 K, and in the $I_2/H_2O$ molar ratio of $0.094{\sim}0.297$ under a continuous flow of $SO_2$ gas. As the result, sulfur formed predominantly with increasing temperature and decreasing $I_2/H_2O$ molar ratios. The molar ratios of $H_2O/H_2SO_4$ and $HI/H_2SO_4$ in global system were decreased as the more side reaction occurred. A side reactions did not appear at $I_2/H_2O$ molar ratios, saturated with $I_2$, irrespective of the temperature change. We concluded that it caused by the increasing stability of an $I_{2x}H^+$ complex and a steric hindrance with increasing $I_2/HI$ molar ratios.