• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.323-323
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• 2012

We present ferroelectricity of Bi-doped ZnO film probed by piezoresponse force microscopy (PFM), which is one of the Scanning Probe Microscopy techniques. Perovskite ferroelectrics are limited to integration of devices into semiconductor microcircuitry due to hard adjusting their lattice structure to the semiconductor materials. Transition metal doped ZnO film is one of the candidate materials for replacing the perovskite ferroelectrics. In this study, ferroelectric characteristics of the Bi-doped ZnO grown by pulsed laser deposition were probed by PFM. The polarization switching and patterning of the ZnO films were performed by applying DC bias voltage between the AFM tips and the films with varying voltages and polarity. The PFM contrast before and after patterning showed clearly polarization switching for a specific concentration of Bi atoms. In addition, the patterned regions with nanoscale show clearly the local piezoresponse hysteresis loop. The spontaneous polarization of the ZnO film is estimated from the local piezoresponse based on the comparison with LiNbO3 single crystals.

• ETRI Journal
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• 제34권6호
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• pp.800-806
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• 2012

Transmission performances of direct detection-based 100-Gb/s modulation formats are investigated and compared for metro area optical networks. The effects of optical signal-to-noise ratio sensitivity, chromatic dispersion, cross-channel nonlinearity, and transmission distance on the performance of differential 8-ary phase-shift keying (D8PSK), differential phase-shift keying plus three-level amplitude-shift keying (DPSK+3ASK), and dual-carrier differential quaternary phase-shift keying (DC-DQPSK) are evaluated. The performance of coherent dual-polarization quadrature phase-shift keying (DP-QPSK) with block phase estimation and coherent DP-QPSK with digital differential detection are also presented for reference. According to our analysis, all three direct detection modulation formats could transmit a 100-Gb/s signal over several hundred kilometers of a single-mode fiber link. The results also show that DC-DQPSK outperforms D8PSK and DPSK+3ASK, and the performance of DC-DQPSK is comparable to that of coherent DP-QPSK with digital differential detection. The maximum transmission distance of DC-DQPSK is over 1,000 km, which is enough distance for metro applications.

• IMMUNE NETWORK
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• 제10권6호
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• pp.206-211
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• 2010

Background: Dendritic cell (DC)-based tumor vaccine is an attractive modality for the treatment of colon cancer because it has been recurred and produced few side effects in patients. Secretory glycoprotein 90K has been found at elevated level in various cancer tissues and sera. We investigated to establish a more effective DC vaccine for the treatment of colon cancer in which the levels of 90K are elevated. Methods: We obtained the concentrated 90K from 293T cells stably expressing 90K. DCs were cultured from peripheral blood monocytes, and a DC vaccine pulsed with tumor lysate was compared with a DC vaccine pulsed with 90K. We measured the functional activity for CTLs by using IFN-${\gamma}$-enzyme linked immunoabsorbent spot (ELISPOT) assay. Results: DCs pulsed with tumor lysate+90K exhibited the enhanced T cell stimulation, polarization of $\ddot{i}$ T cell toward Th1. The CTLs generated by DCs pulsed with 90K efficiently lysed HCT116 cells. The results indicate that 90K-speicifc-CTLs can recognize 90K proteins naturally presented by colon cancer cells. Conclusion: Our study suggests that 90K-specific CTLs generated by 90K-pulsed DCs could be useful effector cells for immunotherapy in colon cancer.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 추계학술대회 논문집
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• pp.183-187
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• 2008

This paper describes a power control scheme to improve the performance of a fuel cell battery hybrid power source for residential application. The proposed power control scheme includes a power control strategy to control the power flow of the fuel cell hybrid power system and a digital control technique for a front-end dc-dc converter of the fuel cell. The power control strategy enables the fuel cell to operate within the high efficiency region defined by the polarization curve and efficiency curve of the fuel cell. A dual boost converter with digital control is applied as a front-end dc-dc converter to control the fuel cell output power. The digital control technique of the converter employs a moving-average digital filter into its voltage feedback loop to cancel the low frequency harmonic current drawn from the fuel cell and then limits the fuel cell output current to a current limit using a predictive current limiter to keep the fuel cell operation within the high efficiency region as well as to minimize the fuel cell oxygen starvation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.309-312
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• 2002

Ferroelectric $Sr_{0.3}Ba_{0.7}Nb_{2}O_{6}$ (SBN30) thin films were deposited on Pt/Ti/$SiO_{2}$/Si(100) substrates by ion beam sputtering. During annealing treatment at $750^{\circ}C$, poling was attempted by applying dc voltage bias across polished surfaces. Phase relation, microstructure and crystallization behavior were examined using XRD and FE-SEM. Ferroelectric hysteresis characteristics were also determined where both remanent polarization and coercive values decreased with the increase of bias voltage. The measured remanent polarization and coercive field values at 5 V and 10 V bias were $36{\mu}C/cm^2$, $10{\mu}C/cm^2$ and 100kV /cm, 80kV /cm, respectively.

• 한국광학회:학술대회논문집
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• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
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• pp.230-231
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• 2001

Silica glass is a core material for optical fiber in optical telecommunications, but its centrosymmetry eliminates the second order nonlinearity. But it is experimentally well known that the space charge polarization induces the Second Harmonic Generation (SHG) when a strong DC voltage is applied to silica glass for a long period time with metal blocking electrodes. In this research, a theoretical calculation of the nonlinear optical property caused by the space charge polarization is performed, and a model of a numerical analysis to predict the small change in nonlinear optical property as functions of time and space is provided.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1939-1941
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• 2000

Nondestructive and destructuve insulation tests were performed the high voltage rotating machine in the local thermal power plants. Nondestructive tests include measurements of insulation resistance. polarization index, AC current. tan$\delta$, partial discharge. Destructive tests include measurements of AC hipot and DC hipot. This paper propose to establish the insulation diagnosis cycle for high voltage rotating machine.

• 한국재료학회지
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• 제24권2호
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• pp.105-110
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• 2014

The aim of this work was to investigate the effects of electrodeposition conditions on the microstructural characteristics of copper thin films. The microstructure of electroplated Cu films was found to be highly dependent on electrodeposition conditions such as system current and current density, as well as the bath solution itself. The current density significantly changed the preferred orientation of electroplated Cu films in a DC system, while the solution itself had very significant effects on microstructural characteristics in a pulse-reverse pulse current system. In the DC system, polarization at high current above 30 mA, changed the preferred orientation of Cu films from (220) to (111). However, Cu films showed (220) preferred orientation for all ranges of current density in the pulse-reverse pulse current system. The grain size decreased with increasing current density in the DC system while it remained relatively constant in the pulse-reverse pulse current system. The sheet resistance increased with increasing current density in the DC system due to the decreased grain size.

• 한국세라믹학회지
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• 제44권2호
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• pp.116-123
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• 2007

Electrical properties of AlN ceramics sintered with 1 wt% $Y_2O_3$ have been investigated. From the impedance spectroscopy, electrical conductivity of grain boundary was found to be much lower than that of grain. DC conductivity measurement showed the electrode polarization effects caused by blocking electrode. The heat-treatment at $1700^{\circ}C$ of the specimen sintered at $1850^{\circ}C$ transformed continuous pain boundary phases along triple boundary junctions into isolated particles in grain comers. The heat-treatment induced decreases both in grain and grain boundary conductivity, and in DC electrical conductivities. From the analysis on the transference number, ionic conductivity was shown to be more dominant than electron conductivity, which was due to ion compensation mechanism during oxygen incorporation into grain.

• BMB Reports
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• 제47권9호
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• pp.512-517
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• 2014

In this study, we showed that Mycobacterium abscessus MAB2560 induces the maturation of dendritic cells (DCs), which are representative antigen-presenting cells (APCs). M. abscessus MAB2560 stimulate the production of pro-inflammatory cytokines [interleukin (IL)-6, tumor necrosis factor (TNF)-${\alpha}$, IL-$1{\beta}$, and IL-12p70] and reduce the endocytic capacity and maturation of DCs. Using $TLR4^{-/-}$ DCs, we found that MAB2560 mediated DC maturation via Toll-like receptor 4 (TLR4). MAB2560 also activated the MAPK signaling pathway, which was essential for DC maturation. Furthermore, MAB2560-treated DCs induced the transformation of $na\ddot{i}ve$ T cells to polarized $CD4^+$ and $CD8^+$ T cells, which would be crucial for Th1 polarization of the immune response. Taken together, our results indicate that MAB2560 could potentially regulate the host immune response to M. abscessus and may have critical implications for the manipulation of DC functions for developing DC-based immunotherapy.