• BMB Reports
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• v.40 no.5
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• pp.656-661
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• 2007

In this report, we describe an optimized method for generation of ephA8 BAC transgenic mice expressing the lacZ reporter gene under ephA8 regulatory sequences. First, we constructed a targeting vector that carries a 1.2 kb ephA8 DNA upstream of its first exon, a lacZ expression cassette, a kanamycin cassette, and a 0.7 kb ephA8 DNA downstream of its first exon. Second, the targeting vector was electroporated into cells containing the ephA8 BAC and pKOBEGA, in which recombinases induce a homologous recombination between the ephA8 BAC DNA and the targeting vector. Third, the FLP plasmid expressing the Flipase was electroporated into these bacteria to eliminate a kanamycin cassette from the recombinant BAC DNA. The appropriate structures of the modified ephA8 BAC DNA were confirmed by Southern analysis. Finally, BAC transgenic mouse embryos were generated by pronuclear injection of the recombinant BAC DNA. Whole mount X-gal staining revealed that the lacZ reporter expression is restricted to the anterior region of the developing midbrain in each transgenic embryo. These results indicate that the ephA8 BAC DNA contains most, if not all, regulatory sequences to direct temporal and spatial expression of the lacZ gene in vivo.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.157-161
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• 1999

We investigated the effect of mechanical back side damage in Czochralski silicon wafer. The intensity of mechanical damage was evaluated by minority carrier recombination lifetime by laser excitation/microwave reflection photoconductance decay ($\mu$-PCD) technique, wet oxidation/preferential etching methods, near surface micro defect (NSMD) analysis, and X-ray section topography. The data indicate that the higher the mechanical damage intensity, the lower the minority carrier lifetime, and NSMD density increased proportionally, also correlated to the oxidation induced stacking fault (OISF) density. Thus, NSMD technique can be used separately from conventional etching method in OISF measurement.

• Journal of the Korean Ceramic Society
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• v.52 no.1
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• pp.9-12
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• 2015

Nano-structured electrodes were fabricated to develop efficient photoelectrochemical conversion systems for the synthesis of hydrogen from water and hydrocarbon fuels from $CO_2$. In this work, we compared the photoactivity of rutile $TiO_2$ nanorods grown on FTO and SEED/FTO by a hydrothermal method. An analysis of the microstructures showed that the density of nanorod/SEED/FTO samples, which showed only the (002) peak in their x-ray diffraction patterns, was two times higher than that of a nanorod/FTO sample. The photocurrent density of nanorod/SEED/FTO samples was increased by as much as 40% of the photocurrent density of the nanorod/FTO sample due to the increased specific density of the nanorods. However, the transient time for a recombination of photogenerated electrons and holes was 20 times faster in the nanorod/SEED/FTO. The seed layers are discussed as possible recombination sites.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.100-100
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• 2009

$TiO_2$ is widely being used as a semiconductor electrode for DSSC. Anti-recombination property and surface area of $TiO_2$ give an important influence to the DSSC efficiency. In this study, $TiO_2$ electrode was fabricated on FTO using screen printing method. Various overlayers were coated on them by dip coating in solution of saturated $Ba(NO_3)_2$, $Mg(NO_3)_2$ and $N_{2}O_{6}Sr$. They reduced the recombination of electrons from photo excited state of Ru dye. The atmospheric plasma treatment was applied to both the $TiO_2$ and each overlayer coated $TiO_2$ surfaces to improve contact ability with dye. We prepared four samples, one sample has bare $TiO_2$ surfaces to improve contact ability with dye. We prepared four samples, one sample has bare $TiO_2$ electrode and the other samples consist of each overlayer coated $TiO_2$ electrodes. We used XRD, FE-SEM, J-V, IPCE and EIS in order to investigate characteristic.

• Journal of Information Display
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• v.3 no.2
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• pp.6-12
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• 2002

In order to achieve white emission from organic light emitting devices (OLEDs), five distinct structures were fabricated and tested. The white emission was obtained using two different color-emitting materials (yellow from rubrene-doped $Alq_3$ and blue from DPVBi) with or without a carrier-blocking layer. For enhancing the red emission, two types of devices with three-color emitting materials were fabricated. The white emission, close to the CIE coordinate of (0.3,0.3), was achieved by using two blocking layers as well that as without a blocking layer. This paper covers the subject of controlling the location of exciton recombination zone. It has been found that there is a trade-off in that the devices with three color emitting layers do not show as much luminescence efficiency compared to those with two color emitting layers, but rather, show distinct red emission in the resultant emission spectra. The highest power efficiency was measured to be 1.15lm/W at 2,000 $cd/m^2$ for a structure with two color-emitting layers.

• Publications of The Korean Astronomical Society
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• v.26 no.1
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• pp.25-35
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• 2011

A diagnostic tool has been proposed to convert the observed surface distribution of hydrogen recombination line intensities into the radial distributions of the electron temperature and the density in HII regions. The observed line intensity is given by an integral of the volume emission coefficient along the line of sight, which comprises the Abel type integral equation for the volume emission coefficient. As the emission coefficient at a position is determined by the temperature and density of electrons at the position, the local emission coefficient resulted from the solution of the Abel equation gives the radial distribution of the temperature and the density. A test has been done on the feasibility of our diagnostic approach to probing of HII regions. From model calculations of an HII region of pure hydrogen, we have theoretically generated the observed surface brightness of hydrogen recombination line intensities and analyzed them by our diagnostic tool. The resulting temperatures and densities are then compared with the model values. For this case of uniform density, errors in the derived density are not large at all the positions. For the electron temperature, however, the largest errors appear at the central part of the HII region. The errors in the derived temperature decrease with the radial distance, and become negligible in the outer part of the model HII region.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.1
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• pp.62-68
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• 2009

Two new generation gap models with modified parent-centric recombination(PCX) operator are proposed. First, the self-adaptation generation gap(SGG) model is a control method that keeps a replaced probability of parents by offspring to a certain level which obtains better performance. Second, virtual cluster generation gap(VCGG) is provided to extend distances among parents using clustering, which causes it to diversify individuals. In this model, distances among parents can be controlled by size of clusters. To demonstrate the effectiveness of our two proposed approaches, experiments for three standard test problems are executed and compared to most competing current approaches, CMA-ES and Generalized Generation Gap(G3) with PCX. It is shown two proposed methods are superior to consistently other approaches in the study.

• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1220-1224
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• 2012

This study examines the photoelectric conversion efficiency of dye-sensitized solar cells (DSSCs) when nanometer-sized Y (0, 0.1, 0.5, and 1.0 mol %)-incorporated $TiO_2$ prepared using a solvothermal method is utilized as the working electrode material. The photoelectric properties of the Y-$TiO_2$ used in DSSCs were studied by frequency-resolved modulated photocurrent/photovoltage spectroscopy. The recombination was much slower in the Y-$TiO_2$-based DSSCs than in the pure $TiO_2$-assembled DSSC. Compared to that using pure $TiO_2$, the energy conversion efficiency was enhanced considerably by the application of Y-$TiO_2$ in the DSSCs to approximately 6.08% for 0.5 mol % Y-$TiO_2$.

• Journal of Hydrogen and New Energy
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• v.32 no.6
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• pp.656-662
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• 2021

For the high efficiencies of quantum dot-sensitized solar cells (QDSCs), it is important to control the severe electron recombination at the interface of photoanode/electrolyte. In this work, we optimize the surface passivation process of ZnS/SiO₂ double overlayers for the enhanced photovoltaic performances of QDSCs. The overlayers of zinc sulfide (ZnS) and SiO₂ are coated on the surface of QD-sensitized photoanode by successive ionic layer adsorption and reaction (SILAR) method, and sol-gel reaction, respectively. In particular, for the sol-gel reaction of SiO₂, the influences of temperature of precursor solution are investigated. By application of SiO₂ overlayers on the ZnS-coated photoanode, the conversion efficiency of QDSCs is increased from 5.04% to 7.35%. The impedance analysis reveals that the electron recombination at the interface of photoanode/electrolyte is obviously reduced by the SiO₂ overlayers.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.4
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• pp.132-138
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• 2023

Doped and undoped-BiVO₄ samples with different elements (Li, Mg) and amounts were synthesized with a hydrothermal method. The synthesized samples were characterized using various techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis diffusion reflectance spectroscopy (UV-Vis DRS), and photoluminescence (PL) spectroscopy. Photocatalytic activity of the samples was evaluated by measuring the degradation of methyl blue (MB) under visible light irradiation. The results indicated that the incorporation of Mg and Li into BiVO₄ caused lattice distortion, the presence of surface hydroxyl groups, a narrower band gap, and a reduced recombination ratio of photo-induced electron-hole pairs. Notably, the photocatalytic activity of Mg5%-Li5% co-doped BiVO₄ sample exhibited a significant improvement compared to that of undoped BiVO₄ sample.